Okay, the way I have a very hard to beat team is:

First use the 'All Characters' cheat.Then pick Ghost Rider. Level up his Penant Stare, Flechette Chain, and Damnation as much as possible. Next, you pick Doctor Strange. Level Up whatever you want on him. Next is Silver Surfer. Make sure you level up his 'Molecular Mix-up' and basic energy beam. Lastly, pick Spider-Man. Level up any long-range attacks from him. Those are good. I beat the game seven times in one day with this team.