Which open world game should I get

Hi guys,
I'm looking for an open world game to buy and cannot decide what to get.  The three games I am most interested in is Assassins Creed 2, Red Faction Guerrilla, and  Prince of Persia (2008). I am looking for the game with the best side missions, a good size and variety of the of the world, and something that has the most lasting value.  I cant seem to figure out what to get. I would love to get some opinions on what you guys think Ii should get based on what I'm looking for. Thanks

I would not say that Prince of Persia meets your requirements at all. Is it only between those three games? Ac2 is great but I wouldn't call the environments varied or the side quests all that interesting. I've not played Red Faction but from what I recall hearing, it might not meet got needs either.

 I guess that Just Cause 2 would be an option but i am the most interested in the three above. As far as GTA, I'm not really into it. 

Check out Saints Row 2. Otherwise I would say go with Red Faction: Guerilla. Prince of Persia is not an open world game.

Assassin's Creed II, best game of 2009. 

Dead Rising 2?

" Assassin's Creed II, best game of 2009.  "

" Just Cause 2      "

fallout 3

" Dead Rising 2? "

" Check out Saints Row 2. Otherwise I would say go with Red Faction: Guerilla. Prince of Persia is not an open world game. "

" from the quick look, I dont really think I would like it "

  Are the Citys In ACII that different from each other?

" @KaosAngel said:

" Dead Rising 2? "

from the quick look, I dont really think I would like it "

I think Just Cause 2 fits what you're looking for. Red Faction Guerrilla was good fun but Assassin's Creed 2 won the much-coveted My Mostest Favoritist Bestest Game of 2009.

" Just Cause 2 seems to fit all the things you want, and it's endlessly entertaining. though apart from that i'm afraid i can't say much about your choices.  "

STALKER: Shadow of Chernobyl. 
  
Amazing game.

Final Fantasy XIII.

The Simpsons: Hit and Run

Just Cause 2 is awesome.  Red Faction has some fun stuff, but it is all rather samey.  ACII is entertaining but the amount of stuff to do runs out faster than some other open world games.  Saints Row 2 is ridiculously fun.  Skip PoP 2008.

Red Faction Guerilla allows you to destroy buildings with hammers.

Personally I think Mercenaries 2 was a more enjoyable game than Just Cause 2 (and they are basically identical, except for that Mercs 2 had more bugs, destructible enviroments and multiplayer co-op), but that was until EA shut down the multiplayer servers.

Red Dead Redemption or Just Cause 2

"  I guess that Just Cause 2 would be an option but i am the most interested in the three above. As far as GTA, I'm not really into it.  "

Just Cause 2 is probably the best sandbox game out there. The story is weak, but who cares about the story when you're given such a freedom of action and a huge world to explore.

Are you open to other game suggestions? I really enjoyed Prince of Persia (2008), but many didn't. It really does hold your hand an awful lot, but if you can overlook that, I think you'd enjoy it. I played Assassin's Creed 2 and I thought it was quite great. Red Faction: Guerilla is okay. The level of destruction you can create is impressive, but overall I didn't think the game was that hot.
 
Anyway, I see you've never played neither Red Dead Redemption, nor Grand Theft Auto IV. If you want open-world games, those are the ones you need to play.

fuck Saint's Row 2 
 
Get Red Dead Redemption

Red Faction.