Fallout games are all pretty rad, and New Vegas is no exception. Since you aren't planning to hook up to the internet, I'd try to get Game of the Year editions when you can, as they will typically include DLC. Hopefully not as a code
The uncharted series is pretty great. Wonderful attention to detail, decent story. It's so cinematic, the wife watched me play the whole thing.
RPGs were handled very well so far, so I'll focus on open world style games.
Red dead would have been my first recommendation, since you said free-world. It's probably my favorite sandbox-style game.
Grand Theft Auto IV Complete edition you can get into for pretty cheap. I said when I played through GTA IV that it was an amazing game engine with a mediocre game played out on it. Lost and the damned, and the ballad of gay tony were much better stories, I felt.
Assassin's Creed is pretty good too, although I'd probably just get the ACII Ezio trilogy, as the AC1 was VERY repetitive. If you LOVE it, then spring for 3, but this way you get three full games for one price. (ACII, Revelations, and Brotherhood)
Arkham City was wonderful, and with 400 riddler secrets to find, you can be busy for a very long time.
I haven't played Far cry 3 yet, but I've heard it's all kinds of open world awesomeness.
Finally, Oblivion/Skyrim are HUGE open world games, with TONS of gameplay. RPG and open world elements here.