BattleTech sourcebooks are usually very cynical, whereas the novels and games are a bit more idealistic. Sourcebooks talk about the huge technological disparity between worlds, where a peasant may have to slave away for years in order to buy something like a microwave oven, while a poor man on the capitals could walk into a store and buy a 10 petabyte hard drive and video player. The series started out much more cynical, during the 300 year long "Succession Wars". After the Wars ended, it became a bit more idealistic. And then slammed right back into the cynical end during the Jihad, when WMD use and total war became commonplace again.
Then again this is only the impression we get from the outside looking in, where we know just how alarmingly terrible the vast majority of the galaxy is. From the inside various factions it is a different story. In no particular order:
For the average Imperial citizen, their experience of life can be truly anywhere on the scale. Some of them genuinely are peasants who toil away and expire completely unnoticed unless they don't pay their taxes or get drafted. On other worlds the experience of life is much more idealistic with freer access to technology and a genuine middle class. Of course they are likely to be idealistic about bringing the light of the Emperor to the whole galaxy, but they do genuinely believe that they and their government is doing the right thing by suppressing discord and killing enemies. The leaders of the Imperium-The High Lords of Terra-are certainly very cynical, but they and a select few others-Inquisitors and Space Marine Officers-truly know the scope of the threats humanity faces and bear the weight of the terrible sacrifices needed to preserve it.
The Eldar are definitely cynics from a traditional point of view, who believe absolutely in putting millions of humans in between them and the bad guys. But then again this is a certain form of idealism. Many eldar characters have been self-sacrificing and are committed to their goals and philosophies.
The Tau by contrast are genuine idealists, and certainly in their original characterization they were doing the right thing, with hints that there was some greater purpose in their actions (forming a 'good' empire that could stand against Chaos and Tyranids), although that has been muddied a bit since then.
The Chaos forces again can be anywhere on the scale. Some of them are cynics who were attracted to Chaos because they wanted the power it offers, while others genuinely believe that the Chaos gods are the true gods of the universe. Anyone who begins to feel the Imperium is a bad thing invariably is said to have fallen to chaos even if they never worshiped the bad gods. All kinds of rebellions and heresies have had genuinely good motivations get portrayed as being Chaos inspired, or ends up calling on the only people in galaxy who will help a rebel in need.
Most of the other factions have motivations that are too weird to really put them anywhere on this scale. We Have Reserves is certainly invoked by all of them, but Orks and Tyranids just make more guys and both have a gestalt connection, while Necrons self-repair. The Necrons alone could arguably called cynical (The Deceiver anyway) but then again they also have their own motivations and they stick to them.
Orks could maybe, possibly, count as Idealistic to themselves. After all, a galaxy with this much fighting available pretty much has to be heaven. Not so much for everyone else, though, they'll burn through whole planets to get their kicks.
It has gotten to the point were 40K is so over-the-top in how deep in the cynical side the setting is, that it could almost be considered self-parody.
"Legions of Steel", relatively short-lived co-traveller to 40k, has a relatively idealistic take on Humanity who guardedly unite to fight against a world/race/galactic threat. Meanwhile, the rest of the galaxy is a mixed bag.
The "Sahara Incident" presents some interesting questions. The rules of engagement - in fact one of the founding premises of global co-operation - is that uplift, high-tech, powered infantry units are never to be used on Earth itself. Another (yet another?) genocide breaks out in Africa, close to a powered infantry base. A rogue lieutenant musters his troops to put a stop to it. The global president, armed only with a copy of the global charter and a Danish (it was early in the morning), talks the lieutenant down, while a multinational conventional force is put together and deployed to end the carnage.
The Fantasians are fascist, racists and all sorts of others things, but the point is made that the party and the people are not synonymous.
The Galactics and Black Empire are Machiavellian, although each has idealistic factions within it.
Dungeons & Dragons can vary, depending on how much Gameplay and Story Segregation you use and just which parts you segregate. For instance, some people prefer to view the world of D&D in as much of a vein as the dark ages as possible, with hard lives as likely to end in disease and starvation as at the claws of a rampaging dragon. Others prefer to think that the peasants could probably just pool together to buy some potions of Remove Disease and so on. Likewise, you can play your character as righteously slaughtering anything that says it's Evil in the Monster Manual because your character is Good (it says so right on your character sheet), or you can play it as more of a moral choice based on actions taken in the game world (after all, that nest of kobolds lurking in the mountains never did anything to YOU). Even character death can be treated as something serious and possibly deeply traumatizing and affecting for the party... or just something that lasts until you can rustle up 5000 gold worth of diamonds.
And that's not going into the actual published campaign settings, from the idealistic heroism of Points of Light or the deeply cynical survivalism of Dark Sun.
The Book of Exalted Deeds, by the way, goes straight to the Idealistic end using that special Monk ability that lets you jump as far as you want. It has a reformedmindflayer.
Bear in mind, hanging out at the extreme idealistic end is the entire point of that book. At the other end, there are books like the Book Of Vile Darkness and Elder Evils.
The sourcebook "A Magical Medieval Society" applies someone's medieval history degree to D&D by pointing out that magic would make life more pleasant in the areas of medicine, sanitation, and construction. So D&D's magic concepts applied to reality would count as a fairly idealistic setting as medieval worlds go.
It might be worthwhile to remember that, per the rules, in previous editions characters motivating their slaughter with 'I'm Good, they are Evil!' are committing Fantastic Racism (a non-good thing) unless it is warranted, IE, unless the races they are killing are Always Evil. It is at this point that the DM notes that the plurality of 'evil' races in the monster manual are, in fact, not Always Evil, and that killing innocents is an evil act...
Surprisingly, the Gothic Horror setting Ravenloft has its idealistic moments, especially in the White Wolf incarnation. The world is a bad place, but there are higher powers seeing that evil is punished and good has a chance. This is a common theme in horror; when there's nothing to lose, Darkness-Induced Audience Apathy kills the horror mood, so there must be something worth saving.
Plane Scape was on the extreme side of cynical. Angels run weapons to demons knowing billions of innocents will die just to keep the demonic hordes in check. A Dickensian nightmare ruled by corrupt philosophic clubs serves as the City of Adventure. There are seven types of heaven, including a supremely dangerous Warrior Heaven and a "nature red in tooth and claw" heaven where sapient animals eat each other. There are seven distinct hells, one of them possibly infinite. It's played for Black Comedy.
The World of Darkness series, both Old and New, sits heavily on the cynical side. Given that its premise is that it is the real world but Darker and Edgier, that's not really surprising. One of the uniting themes of all of the WoD games is the grinding down of idealism into a nub of cynical apathy. Practically every idealist that the books talk about either ends up broken and empty or destroyed by their beliefs. While a lot of characters still claim a certain sense of commitment to a cause or ideological faction, the focus on violence as a means to solve problems as well as any number of forms of mind control and reality distortion means that they are going to become pragmatic if they want to keep showing up.
On the other hand, Wraith The Oblivion doesn't so much sit at the extreme cynical end of the scale, it punches through said end and keeps going into the cynical direction with seemingly unlimited momentum. It speaks volumes that this is a game that has actually had a few cases of induced depression (yes, clinical depression) in sensitive people merely by playing it.
It is safe enough to say for the sake of the Endless Warfare, all Tabletops have to be naturally cynical in nature to perpetuate eternal conflict.
Flames Of War and Axis And Allies are both miniatures warfare games set in World War II. They are neither cynical nor idealistic, with the war crimes of the Axis and Allied powers are both glossed over in favor of a purely military exercise. Quite a number of table top space naval battle games have been set in the Star Trek universe, which is widely loved because it is so idealistic. Star Wars is a romantic, idealistic space opera and has spawned quite a few miniatures battles games. Avalon Hill is the most famous producer of other war games which take a neutral stance toward their topic, but there are many. So...no, they don't.
Rym leans hard to the cynical side, what with multiple apocalypses, genocidal alien necromancers, and an empire pretty much devoted to enslaving and exploiting everyone else. And in the middle of all this is a tropical island chain of Purity Sue otter-people. Author Appeal comes to mind.
Pathfinder's default setting of Golarion leans towards cynicism in the current timeline — one of the gods died a century ago (after he was about to make his big second coming), prophecy no longer properly works, the remnants of one powerful empire is now openly ruled by devils while another is on the verge of collapse. Most of the explicitly 'good' nations are either isolationist or too focused on containing/combatting a specific threat to make the world better. However, from a meta perspective, this cynicism serves a purpose: once, when someone on the Paizo message boards commented on how many of the more powerful nations are evil, one of the developers said something to the extent of "Gee, one would almost think the world might need some heroes to come save it."
So far, every Adventure Path has been idealistic. Something really bad starts happening. Heroic player characters step up and change the world for the better. Rinse and repeat. Some are more idealistic than others. Jade Regent, for example, is fundamentally a romance mixed with an Arthur story. Skull and Shackles expects the player characters to be pirate anti-heroes.
KULT is another example of a very cynical setting.
Paranoia is too busy being a satire with Comedic Sociopath heroes to really be cynical, because when you play a police state worse than Orwell's 1984 for slapstick comedy, it's hard to take seriously. Taking the setting on its own terms, it's possibly more cynical than Warhammer, seeing how at least Warhammer has individuals heroically and futilely trying to hold back the darkness. There are no good people in the Crap Sack World of Paranoia. Inserting the obligatory joke about treason is treason.
Decipher's Lord of the Rings RPG expects the players to be damn heroic. It's on both the Idealistic and Romantic side. Iron Crown Enterprise's LOTR game was also idealistic, but less so.
West End Games' old Star Wars RPG and the D20 versions are both fairly idealistic. Sure, there's plenty of bad things in the galaxy far, far away but it's still Star Wars' heroic Space Opera.
Continuum is idealistic. The player characters are time travelers who fight for an organization that defends the timeline which allows humanity to eventually Ascend to a Higher Plane of Existence from time travelers who would use their power for themselves at the expense of the greater good. Individuals may come and go, and people -will- suffer, but the war is definitely won by the good guys and humanity certainly ascends (they can travel time). Of course, other time travelers are very hesitant to tell you too much about what you will do and suffer in the war, because then you might try to change it, and then they'd have to fix the timeline from your meddling.
Over the Edge is set in a dysopian city of conspiracies and nastiness. Highly cynical.
Unknown Armies is moderately cynical. You are expected to play in a modern horror setting which self-identifies as a post-modern game of power and consequences, but you are supposed to play someone who cares about what's going on and is trying to do something with it. Anyone who can work magic must be crazy-obsessed but not necessarily evil. Humanity is the ultimate force in the cosmos and there's something mysterious happening that could lead to Armageddon or our apotheosis.
Net Runner, Cyberpunk 2020, and Shadow Run are set in a cynical dystopian Cyberpunk settings. This should come as no surprise, as cyberpunk is almost always cynical and usually dystopian.
Shadow Run style of cynicism is based on how far out of depth is the average Shadowrunner is facing the nature of eons long plots, unspeakable horrors and the local watering hole of Shadowrunners being slowly replaced with more sociopathic, morally bankrupt (even as a shadowrunner) users as every sourcebook takes the worst case scenario for the next edition.
Stars Without Number takes a middle-of-the-road approach. Human interstellar civilization suffered an unknown tragedy and is piecing itself together, rebuilding Lost TechnologyAfter the End, and trying to reconnect with its various worlds. Relationships between planets are often exploitative, especially if there is a large difference in technological progress, and psychic humans are feared and persecuted. However, there's no existential threat to humanity, aliens are not inherently hostile, and most conflicts are examples of Grey and Gray Morality.
Rocket Age sits somewhere in the middle. On one hand, there is genocide, death camps and Nazis. On the other there are plenty of people working to make the solar system a better place and the heroes are expected to win in the face of insurmountable odds.