1. Fallout New Vegas - if you liked Fallout 3 you will love Fallout New Vegas. Same concept and graphics, better role-play

2. Elder Scrolls IV:Oblivion - there are not many games like the Fallout series to be honest, but try Oblivion if you like Fallout's gameplay and you dont mind fantasy world RPGs.

NOTE: I would suggest Fallout 1 and Fallout 2 as well but i am not sure they will be appealing to majority of the gamers nowadays (due to dated graphics and being PC exclusive). If you think those don't bother you then give the first two games in the series a shot.

EvilSelf...