X-Men Team Up: Colossus and Iceman CPU Co-OP against Anaconda

New boss: Exodus

Mega Man and all bonus stages - Mega Man Robot Master Mayhem fan game

Pudgy Pig Boss Fight: The No Special Weapon Challenge! | Power Rangers Fan Game

I think I already saw this somewhere...

Reinhart Unleashed: The Sorcerer's Path | Pocket Dimensional Clash 3 (OpenBOR)

Mega Man X joins this crazy crossover with Sonic, Castlevania, Castle of Illusion, Dc Comics and more!

Beast and Iceman Fight Spider-Man Villain Trapster

Golden Axe 3 stage

New boss: Mr. Negative