InFamous - Be Good or Evil based off your choices, and it changes your appearance and how people look at you (you're great! you're horrible!)
Oblivion - You can be good or evil, but people don't really look at you differently and nothing in the world really is massively changed if you are Satan's twin brother. Very huge world though, and can easily take dozens and dozens of hours to finish. BTW, has swords, magic, stuff like that.
Fallout 3 - Kinda like Oblivion (made by the same people, Bethesda), but the way you act and the choices you make cause a bigger impact on the world and the people then in Oblivion. Post-apocalyptic world, with bandits, giant scorpians/cockroaches, guns, explosions, etc. Can also spend a long while on the game, but some people think exploring is a bit less fun in Fallout 3 then in Oblivion.