Biggest bang for your buck?

[ckmlb]

World of Warcraft- 50 dollars then 15 dollars a month and you can play it without ever playing another game again if you wanted.

Oblivion- over 200 hours of game easy for 60 bucks.

Any game that you can play online repeatedly forever (shooters, Battlefield 2 is a great example, my favorite multiplayer shooter ever).

I mentioned WOW separately because I think it's the only game you can play exclusively for like a year and not get bored of it no matter how much you play.