Elder Scrolls IV: Oblivion. Just a MASSIVE world. With AMAZING graphics. A BILLION missions. COUNTLESS random mines, caves, forts, etc., each with its own story. And last but definitely not least, the people!! there are so freaking many ppl in that game, each with their own name, face, personality. The only bad thing about that part of the game is that they only had a few voice actors/actresses, so alot of the ppl sound alike XD. But just the fact that u can talk to everyone in the game, and they all have a house, a schedule(places to go.) They dont just stand in the same spot all day and night not moving like other games(final fantasy). Overall this game will keeps u busy for 200+ hours at the very least. 1,000,000,000/10
There seems to be a problem here, some people are saying Oblivion and Guild Wars and such, but the correct answer is Resident Evil 4, a game that will never be matched, ever, by any other game, in any of the fields of gameplay, replay value, originality, customization options, and any other thing like that I can't really think of right now.