I'm gonna say this- The Power Rangers game was one of the BEST sidescrolling fighting games I have ever played, and it's two player. Not kidding, I had a blasty.
Of course Sonic games, especially when you have the game plugged into the Knuckles cartridge plugged into the Sega. THAT was innovation, friends.
Battletech got me into Mech games.
Sunset Riders
Jurassic Park
And many many more.