I have a difficult time ponying up $50 for a new game without having played it before, and renting games costs like $7.50 each, after which, if you like it, you still have to come up with $50 to buy the thing.
For those in my boat, check out
GameFly - it's like
NetFlix, but for games, and you can buy their used games for cheap, cheap, cheap. I bought my copy of
God of War from them for $28 - with free shipping - and the cheapest I can find it used is $40 right now. And I'm not even a GameFly member! If you are a member, you can rent the game using your membership and they have a "Keep It" price which is significantly less than the cost of the game new (usually by about $10 at least). For the avid gamer, definitely something to look at.