Fallout Series (1,2,3, New Vegas, Oblivion, Morrowind) all good. Yes, can get dull at times traveling in their worlds, but interactive SP play is worth it. Not to mention the Mod community for Fallout and Oblivion that provide addons, upgrades and creativity. Also worth noting the mod community for the Half Life/Half Life 2 (origin of Counterstrike), plus all the addons (e.g. Gary's mod) and various scenarios based on the HL engine . If you have a good thing, gamers and independent developers will keep supporting the game and keep you coming back.