The only co-op I'm aware of for the 360 is Halo' sadly. But I suppose since the Wii has come into play, I can name a few on that.

The first 2-player co-op game I think of is Resident Evil: Umbrella Chronicles. Unlike how the title implies, it is not scary, at all. It's a light-gun game, though it's pretty fleshed out in comparison to some others. The game covers the story of Resident Evils 0, 1, 3, as well as some things that didn't appear in the games. At the start of each stage, you choose between the male or female character of the chapter, and then one of the weapons you've found from breaking objects in the past. Breaking objectx reveals goodies, of course. There are 9, main co-op missions, but the bonus missions can be made into co-op missions later on.

Another light-gun came (which has you aim at the T.V. if you wish, unlike in RE) is Ghost Squad, an arcade port for the Wii. It has some extras, but I honestly don't know what they are, as I've not bought the game.

Another one which comes to mind is Metal Slug Anthology, which as the name implies, is a collection of Metal Slug games. Metal Slug is mostly comparable to Contra, as you go from left to right killing things until you reach the end and fight a boss. Naturally, as with all games of this genre, there's co-op. Keep in mind, this also came out on the PS2.

There are more than a few good VC co-op titles, but with your PC's, you could probably already play them with ROMs and an internet connection. →,→

And, of course, there's Wii Sports, which comes with the system. It contains Tennis, Bowling, Golf, Baseball, Boxing, and 3 training games for each. You'll likely only play one of these, which is what everyone seems to do.

Also, if you get s Wii or 360, keep in mind that they are backwards compatible. If you didn't have the system they're backwards compatible with, you should look into the games that those systems have.