Marvel:
- The Thing - it seems baffling that the Fantastic Four didn't make it into any Marvel vs. Capcom game. The Thing could mix boxing and wrestling moves into his attacks, along with calling the other FF members for assists. (plus, it would be great to hear "it's Clobberin' Time!")
- Scarlet Witch - she was one of the main Avengers in the Busiek/Perez run, which had started around the time that development would have begun (that run started in 1998). I was torn between her, She-Hulk, and the Wasp for this spot, but Wanda seemed to have a bigger role early on.
- Nightcrawler - the X-Men were huge in the 90's, and Nightcrawler seems like one of the most popular members who didn't make it into one of these games. (then again, I didn't think of Jean until after I typed this)
- Black Panther - the Christopher Priest run started in 1998, which helped to reinvent the character, and I'd be interested to see how the developers could incorporate Wakandan tech into his moves. (it was either him or Ms. Marvel, a.k.a. Carol Danvers, since she was on the Busiek/Perez Avengers team and she had ties to the X-Men; I could easily picture either of them being in)
Capcom:
- Zero - while there were four Mega Man characters in MvC2 (Mega Man, Roll, Tron Bonne, and Servbot), it feels odd that the X series didn't get any attention when it came to the roster. X or Zero could work, but Zero's more visually distinct.
- Tessa - I wanted to incorporate a character from one of Capcom's lesser known fighting games like Red Earth, though presumably she'd be using new sprites to match the style of MvC2.
- Mike Haggar - there are no Final Fight characters in MvC2, which seems like an oversight. I get that Mike Haggar would have some similarities to Zangief, but having the two of them face off seems like one of those "dream match" kind of things that weirdly hasn't been fulfilled yet
- Jon Talbain - Darkstalkers characters seem like they'd make the transition to MvC easily enough, and Talbain's a kung-fu-using werewolf.
Admittedly, some of my list was likely inspired on some level by the Marvel Cinematic Universe and/or Marvel vs. Capcom 3. (I feel like it would be tough to completely avoid those two as sources of inspiration) I probably should have tried to come up with at least one unorthodox character, like how Shuma-Gorath was picked because he was distinctly non-humanoid, but I couldn't think of one off the top of my head.