These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Author's Saving Throw: Possibly the reason why this game exist in first place is because Capcom (a Japanese company) needed to give Japanese players something to be excited about/something they could relate to, rather than using characters from American comics.
Big Lipped Alligator Moment: Most endings in Cross Generation of Heroes do not mention the final boss fight at all. Those falling outside the "Most" are Roll, Yatterman-1, Volnutt, Karas, Jun, and (especially) Viewtiful Joe's. In Ultimate All-Stars however, everyone refers to Yami directly or indirectly — either they contemplate on them defeating the final boss, or recovering from the reality warp that took place during the game (which apparently is the "real" plot).
Ear Worm: Ultimate All-Stars doesn't have the character themes anymore, but damn, the Orbital Ringstage music is really catchy, in a retro-techno sort of way.
Both versions of "Across the Border" are pretty catchy as well.
Saki not only has ascended from being an extra in Quiz Nanairo Dreams, but for Ultimate All-Stars, she received a lot of buffs.
Frank West who apparently made the game a day-one purchase for most fans.
Zero and Joe the Condor, who are really popular characters in their original works; Zero is even more loved than Mega Man himself.
Doronjo, who thanks to her massive popularity in Japan, she was the most requested character during the location tests, and when she was revealed during SBO 2008, the crowd cheered. This makes her the only playable villain character appearing in the game.
Both Yattermen, who, along with Doronjo, represent the most popular Time Bokan entry, making many people to wonder why the original Time Bokan barely appears as a reference, yet Yatterman characters are always referred when people mention Time Bokan.
First Episode Wins: Wondering why Yatter-Wan spits out little crocodiles instead of something else in Yatterman-1's level 3 super? That's because it's what the robot dog did in the very first episode of the Yatterman franchise as a whole.
Fountain of Memes: Frank West is likely to become this. More so than in Dead Rising, even. THAT'S HILARIOUS!
Hilarious in Hindsight: The game's intro song is called "Across the Border." It is effectively making a jump across the border overseas.
Memetic Badass/Iconic Outfit: Hurricane Polymar. He's the guy who beats up people in spandex while wearing spandex with a thong (not an underwear!) outside of his suit and a white crest that has an arrow pointing down to his crotch—all while yelling out like Bruce Lee.
Rescued from the Scrappy Heap: Roll. She's no longer a weaker clone of Mega Man, and has attacks that actually prove quite useful if you know your way around. In-universe, her opponents' win quotes are rather respectful towards her.
Scrappy Mechanic: If your opponent quits or rage quits in an online match, you lose.
PTX-40A and Gold Lightan are giant characters whereas Roll and Viewtiful Joe are tiny characters. Some attacks will be different because of it... particularly Alex's Stun Gun Headbutt... especially when doing it on Gold Lightan. Just... just look at it...
Lightan's command grab to another robot. Watch him slam the foe to the ground and body-rape the poor mecha!
Tear Jerker: Frank's ending, when you think about it, he's thinking back to when he helped the heroes... But remember his final fate in the game he's from? It becomes bittersweet in hindsight.
Luckily, Dead Rising 2: Case West confirms that Frank's OK.
The ending for Viewtiful Joe. It has him beating Yami, than getting sucked back to his dimension. The other heroes talked about how big of a chatterbox he is, but overall, really liked him and knows that this isn't the last time they see him. The ending picture of Joe on the brink of tears as he looks in the store window seeing the heroes he met in the other world stopped me cold. Imagine yourself fighting along the heroes, beating them, and saving the world, than imagine yourself being sucked back to your dimension by force, probably never seeing them again. Really makes you think, especially if you are a okatu like Joe.
They Changed It, Now It Sucks: Within Ultimate All-Stars, people who have played the original version felt that the removal of character themes was a bit harsh as well as some character changes, specially Karas. He was a powerful character in Cross Generation of Heroes, then he was nerfed for Ultimate All-Stars, for balance reasons, leading to massive complaint about this. Now that the game came out, people are whining about the removal of most mini-games and the animated endings. They suddenly forgot the fact about the new characters, stages, the rebalanced metagame, and the very fact that the game is now available in the US and in Europe. And then we have the art. UDON has stated that they did redo all of the ending artwork (not the animated ones) for all characters and for the newcomers. Cue people angrily complaining about the change and how the style sucks.
Tier-Induced Scrappy: Karas in Cross Generation of Heroes, reported by many people. Only In America, though. Japan has pretty much gotten over it since SBO 2009, and everyone plays nearly everyone in the game. Heck, PTX-40A gets quite nice attention too!
And now, with Ultimate All-Stars, it seems that this has fallen on Zero.
To a somewhat lesser (but still noticeable) degree, Tekkaman Blade gets this kind of ire too. God forbid that you use them together.
Gold Lightan was apparently tournament-banned.
Unexpected Character: NOBODY expected that Tatsunoko would be the next company Capcom would pick a fight with, so their entire roster counts as this. As for the Capcom side though, most of their roster was also quite unexpected:
Megaman Volnutt getting in over the original Megaman or even X.
Batsu Ichimonji making his long-awaited VS. series debut.
Soki as an Onimusha representative, over the series' main protagonist Samonuske Akechi.
Saki, at least for overseas players, as her origin game was a Japan-only arcade quiz game. Her only appearance before was an assist in the first Marvel vs. Capcom game.
Frank West, although he did end up being the number one reason why American gamers picked the game up.