Marvel

Thor
Thor is my 3rd favorite Marvel heroes and it always irked me how he is the only primary member of the Avengers yet to be a playable character. The guy is a total badass and I'd love the chance to use him in a fighter. I'd either want them to use the Classic Thor outfit because it still looks cool all these years later or his Ultimates outfit because there is an awesome simplicity to it.

Moon Knight
He isn't very mainstream from what I gather but all the same Moon Knight is my second favorite Marvel hero. An all around awesome character whose current run in comics has been one of my recent favorites in all comics. I just want to see him in because I'm a fan but I also think his combat style could be very refreshing. He's a rough and tumble brawler really and I think a brutal ass kicking would be a welcome change of pace from all the laser beams and stuff we'll likely see in this game.

Deadpool
He's my all time favorite Marvel character. Tons of people are clamoring for him. My reasons are basically the same as everyone else. Including Wade should be a no brainer.

Juggernaut
I always liked Juggernaut a lot. I think his powers are awesome and his personality is also really neat. Go figure that the invincible avatar of an ancient god of destruction is actually a pretty down to earth guy. I'd like to see him make a return but I hope they overhaul his moves because he was kind of bland to use in the last game I think.

Dr. Doom
He's one of the greatest villains in Marvel as well as comics in general. He deserves to make a return. He is also wanted because he would at the very least make a good representative for the Fantastic Four. You can't really have any one member from the FF because the whole idea is they're a team, so why not just use their greatest enemy instead. Doom is just cool and a marvel icon. If we want villains in the game he should definitely be near the top.
Capcom

Dante (Devil May Cry)
Kamiya's wishes be damned. Dante isn't your property anymore. Let him be in crossovers! Seriously. In the short time he's been around Dante has become one of gaming's most recognizable, beloved characters as well as a Capcom icon. He revolutionized the action genre. That his only crossover appearances to date were in an RPG and a card battle game to me is baffling.

Gene (God Hand)
God Hand is a cult favorite that was all about the martial arts. Gene had I believe a couple hundred moves you could use to customize his movelist with so Capcom has a huge pool to draw from if he was in a this game. The game seemed to draw a lot of inspiration from Fist of the North Star but was very comical and zany. I think that unique and nutty martial arts action would be greatly welcomed to a roster.

Phoenix Wright (Ace Attorney)
This could be epic. People have wanted to see Phoenix in a game since SSBB. The way I see it he could summon friends for specials like Captain Commando. I think he'd make a great comic relief character as well as an epic addition in general.

Rad Spencer (Bionic Commando)
I love Bionic Commando and I know a lot of people still consider it a classic. Despite the new 3D one being a commercial flop, "Rearmed" was extremely successful. Enough so that Capcom have actually green lit a sequel so you know BC is still on their mind. I think Spencer could be this "retro" character of this game. Kind of in the same vein as Strider and Captain Commando. Gameplay wise he could borrow a bit from Omega Red.

Date Masamune (Sengoku Basara)
I've only had a brief chance to play the poorly localized version of Sengoku Basara called Devil Kings. Even that I though was pretty fun. It's basically Capcom's take on Dynasty Warriors and I think it's better. Either way, the series is pretty popular in Japan and it looks really cool in action. The way I see it, Onimusha had a turn in TvC, so lets let a different Capcom samurai be in this one. There was already a Sengoku Basara fighter anyway so they have a good starting point.