The answer depends on where the series falls in the Sliding Scale of Idealism Versus Cynicism.
A story can be idealistic or cynical towards any idea. In general, if the story values or is hopeful for a particular ideal, then it is idealistic. If the story criticizes, assaults, and accentuates the negative about that expectation, then it is cynical.
For a simple, archetypal example, let's assume that the idea to believe in is Humans Are Good/Rousseau Was Right. In idealistic series, those who believed it got lots of friends and a Happy Ending (therefore, Right Makes Might), while cynical series are Crapsack Worlds where those who believed it got ruthlessly bullied by everyone else (therefore, Might Makes Right). Of course, the definitions of "Right" and "Crapsack" in the above can technically mean whatever one wants them to mean.
However, be careful not to confuse idealism with straw optimism, cynicism with straw pessimism (or realism, for that matter), and the scale as a whole with the Sliding Scale of Silliness vs. Seriousness. Also note that when this applies to characters, this does not mean good or evil. After all, it's perfectly possible for an idealist to be evil, and a cynic to be good. Likewise, a very cynical series could be quite lighthearted (see also: Crapsaccharine World), conversely a very idealistic series could be extremely dark. It's also true that comedies can be cynical as all hell (see also: Satire), and dark dramas can end idealistic (see also: A World Half Full).
See also: The Idealist and The Cynic for the archetypal characters. Less sane characters fit in this scale in their own way, with a Cloudcuckoolander or a Loon with a Heart of Gold leaning towards the Idealism side. For how both sides often portray each other, see Wide-Eyed Idealist/Silly Rabbit, Idealism Is for Kids!, and Grumpy Bear/Silly Rabbit, Cynicism Is for Losers!. See Cynicism Tropes, and Idealism Tropes for lists of each.
This particular sliding scale can be the topic of fierce debate. Each person will have a different point which they tend towards. Therefore, this scale is most useful in targeting demographics and those who are sympathetic to a certain world view, and identifying where on the spectrum one's own work is.
Cerebus Syndrome describes a shift from comedy to drama and this often also results in a shift from idealism to cynicism. Reverse Cerebus Syndrome is the inversion. When shows Zig Zag between the two, they're on a Cerebus Roller Coaster.
- Animated Films
- Anime & Manga
- Comic Books
- Fan Works
- Live-Action TV
- Newspaper Comics
- Recorded and Stand-Up Comedy
- Tabletop Games
- Video Games
- Web Original
- Western Animation
- Silver Crisis has a huge part of the story focus on whether Strength comes from raw power, or from your own will/mindset and the help of others. The Scale slides towards the Cynical Side for most of the plot, with moments such as Lucass constant losing streak and status of being a burden to Lucario, Silver and Ganondorfs Overwhelming Power, and the Corruption of Lucarios former trainer in pursuit of this leaning on the side of Raw Power means everything. But by the end of the story, the scale lands firmly on the Idealistic side, showing that the trust Lucas and Lucario had for one another is what truly defeated Silver, as well as Lucass strength of heart and willingness to better himself being what allows him to truly unlock his hidden power and become truly strong.
- Swan Song starts off very, very cynical and keeps going downhill, with worse and worse actions being taken and more and more tragedy happening as it progresses. While some heroic characters exist, don't expect them to actually make anything better. Until the true ending, where things are hopeful and finally improving, at least a little.
- While Muv-Luv Unlimited is mixed but ultimately idealistic, its sequel, Muv-Luv Alternative, as well as anything else that takes place in the Unlimited verse, is very cynical and painful, dealing with nationalist humans waging a civil war and actually fighting the BETA after them being hyped up but unseen in Unlimited. Rather than learning that humanity is losing miserably against them, you're seeing it firsthand, and only very rarely does something actually go well. In the end, it's on a mixed note. The BETA's leader has been removed from Earth and valuable information has been uncovered about them, but the moon and Mars are still heavily populated by them and there's 10^37 (or 10000000000000000000000000000000000000) total other worlds the BETA inhabit. Yuuko estimates that an additional 30 years has been bought for humanity as a whole by the events of Alternative, too.
- Songs And Flowers, while it can be mixed and does delve into serious subjects, particularly the discovery that the protagonist's Missing Mom was actually murdered, it's much closer to the idealistic end with its emphasis on friendship, love, support, and personal growth.