is classic MM or X that much different?
Well, they're two different robots to begin with.
I always liked X better since he catered to an older fanbase as his world was so much darker (dealing with death and all that) while Mega Man was family friendly. As stated above also, X could think for himself, had Ultimate Armor, more abilities, and could use a sword whenever Zero died (which is why I'm fine with Zero as X since its basically a compromise from Capcom).
I really think Silver Surfer could be a cool addition. Dat, Power Cosmic.
Me too, but for whatever reason, Marvel didn't want him playable in the game so they gave us the lame ass Evil Alliance members as Galactus' Heralds fight instead.
My Eight:
Capcom: Mega Man, Ruby Heart, Bison, and Pyron.
Marvel: Juggernaut, Psylocke, Gambit, and Venom.
Honorable mentions:
Jedah, Fokker, Leo, Alex, and Soki
Blade (even if he was just Marvel's version of Dante), Blackheart, Thanos, Dr. Octopus, and Moon Knight.
Although I wouldn't be surprised if Bulleta (B.B. Hood), Colossus, Gambit, Hayato, Mega Man, Psylocke, Rogue, and Ruby Heart were The Eight Nitsuma was referring to since they were revealed to still be alive.