A Decent 2 Player Co-op game?

[Synthesthesia]

N+ is a great co-op game in my experience, it's good for short little co-op sessions too as a mission can take 10 seconds or a couple of minutes depending on complexity. Cheap too since it's an arcade game. Really hard though, but lots of fun

[ItsThere]

The Red Star is fun in co-op and soon to be getting a Wii release I understand. Can be found on PS2 for £5 in Game.

[Shoju]

One that hasn't been mentioned is Justice League Heroes which is by the same team that made the Champions Of Norrath games and Baldurs Gate Dark Alliance. It's a very similar type of game.

A couple of games with offline co-op that I'm really looking forward to are Fable 2 and Sacred 2 on the 360. Sacred 2 will be like the champions games but I'm expecting it to be far far better.