Need help picking a game!

First post, kinda scared. Anyways, I was wondering, what do you guys think is better, GTA IV or Oblivion: Game of the Year Edition. Can't decide on either one, so I was hoping to get everyone's opinion. I loved Mass Effect, and enjoyed Bioshock. Thanks for all your opinions.

Oblivion is my favorite 360 game and imo one of the best rpg's ever made.

GTA is just okay for me.

I am a big fan of free roaming games, but I've never particularly like the GTA series.

Oblivion will last you much longer. GTAIV is fun for a bit, but once you've played it through once there isn't much replay value - get 100% in one playthrough and thats it.

Oblivion is huge and you can easily play it for 100 hours and not have done half the stuff in the game. Now you can get that in GOTY edition quite cheap, I'd say thats your best bet

Oblivion is alot longer, and there a lot more you can do in Oblivion. So go with Oblivion.