A great team should include at least one character who matches each of the following:

BRAWLER-strong melee and up-front powers, having a ranged attack helps to-mine is Black Panther.

MID-RANGE/ELEMENTAL(element to handle Ulik in Asgard-strong against annoying foes never come near brawlers or enemys to dangerous to approach for any reason-mine is Ghost Rider.

SHARP-SHOOTER-strong long range attacks and/or mid strengh multi hit attacks-mine is Silver Surfer.

WELL-ROUNDED-has powers for all occasions, strong ranged, strong up front, mid-radial, mid-multi hit, basicly all the others in one minus high striking-mine is Iron Man.
It is true shame that none of the flyers have high striking.
If you want details on my team go here. http://www.neoseeker.com/forums/32062/t772186-team-combinations/6.htm

captin america, spiderman, iceman, human torch the kickbutt

Recently, I've been playing with Spider-Woman and Ghost Rider. I can't see why I'd ever need anyone else. One shot=one kill with both of them. Iron Man has the same style power too. I love it. Me and my friend have just been tearing our way through the levels. Our team right now consists of Spider-Woman, Ghost Rider, Cap and Deadpool. We've lost a character only once, when Cap jumped off a cliff. He was comp-controlled. It's totally unstoppable.

To be honest, almost every character on the game can be put together with anyone else and still make a decent team. Well, ALMOST everyone (I'm looking at you, Storm). But IMO the best team has to be:

Ghost Rider
Mr Fantastic
Iron Man
Deadpool

Mr Fantastic is on there because of his godly power with Fantastic Fists - he can just critical everything on the screen to death instantly with the big stompy move - including most mini bosses.

Ghost Rider is also hugely powerful with Ravaging Flame - it's rare to find an enemy that doesn't go down before one-three hits with that move, and Penance Stare means that he is basically never gonna run out of energy.

Deadpool and Ironman or on here because of their buffs - energy reroute means that both of them can use the energy-consuming press and hold moves that make them great, without risk of running low on energy; while Deadpool's battle cry means that both blade cyclone and uni-beam become ridiculously powerful.

THOR *bleep* YES
Thor because he is the god of thunder and friggin war....

Iron Man, Captain America, and Thing because they were alright dudes.

if one died, it was Colossus, Deadpool or Spiderman