Consider this.

Playstation2 is the cheaper. Will play DDR, DVD's and Guitar Hero (I developed a controller for that game, hence the mention.) Outdated tech., but still a great system. No HD capabilities. On-line gameplay possisble with adapter. Will not play PS3 games. $129.00 at BB.

Playstation3 is backwards compatable (PS2 gameplay), has a built in Blue-ray player (lets you watch HD movies on your HD TV with movies marked Blue-ray), will connect to Internet for browsing and on-line gameplay. Can download extra game content for play not available on game disc. HD output. Can load and save entire games from disc. Much more. Basic unit $399.00 at BB.

I'd get the PS3 if you have a HD TV, otherwise get the PS2.

I don't know too much about Wii and Gamecube.