Well there's Skyrim or Fallout like the guywithnopants said. Another option might be Minecraft, a very good time waster.
Civilization 5 if you like strategy games... the best ones are usually open world games where you can screw around for a time and not have to worry about beating the main story and end up stuck wondering what the fuck else to do.

The other option that I can think of (that I've done) is to get an emulator of a console you like and get a collection of old games for it. Replay some old favorites and stuff.

Guywithnopants has been summoned.
Age of mythology.
Command and conquer series.
Company of heroes.
Napoleon total war.
As you can see i love strategy games....

Yup :D Thank to you both :D