Most fun simultaneous co-op games?

[treismac]

Pocky n Rocky (SNES)
Jackal (NES)
Crisis Force (Famicom)
Balloon Fight (NES)
Double Dragon II (NES)
Mario Bros. (NES) and the Famicom Disk update Kaettekita Mario Bros. is even better.
Bubble Bobble (NES)
Rampage (NES) Oh, wait... you said "fun," right? If you want long and monotonous, Rampage is your game.

[o.pwuaioc]

D'oh, just saw that Pocky and Rocky was mentioned. However, Secret of Mana was not. Great co-op game, and is for up to 3 players rather than just 2.