Yeah, I guess I was a little hasty and this has been a stressy week. All the characters I can think of are probably too niche, like Elisa Bloodstone and the Wasp.
Wasp's more high-profile than most. Black Widow would make for a pretty generic fighter, but she WAS in a major Hollywood motion picture recently. Sue Storm's powerset is pretty tough to realize in a fighting game, and anyway the FF are already covered by Super Skrull.
Storm's already been mentioned as the most obvious choice, not only in terms of name recognition but the fact that Capcom's used her in the past. I expect we'll be seeing her any time now.
Me, I'd like to see Songbird.
Lessee...Firestar could work and the audience might remember her from the cartoon. She-Hulk would be good but of course comes with the "female version of a male character" problem. Emma Frost's got the turn-to-diamond thing going on now, so her powerset's no longer impossible to implement in a fighting game.
...and I guess there's Elektra, if you must.
Now I want Nextwave's Captain Marvel in there. Or The Captain. Or anyone from Nextwave, really.
Also spiderman
Still rocking the fugly Todd McFarlane design. Could someone please give Capcom a comic book from the last decade?