Oh man, if you never played through HL2, DO IT. Also, Oblivion is still one of the best games ever created, as long as you mod it up a little. Keep in mind that if your computer is for shit, you can get mods to reduce the graphic quality down significantly so it plays smooth.

Also, it's kind of fun as hell to play the game with a low visible distance. The fog effect is kick ass! I highly recommend it. Also, take the grass slider down to zero, that will net you a solid 5-10 FPS alone.