Here are the best i've tried although they are a bit high requirements:
TES 4 - Oblivion: Probably the greatest RPG to date. It's the sequel to the equally great game
TES 3 - Morrowind. If you're not familiar with the series, or if your hardware is not up to date, I recommend you start with Morrowind.
www.theelderscrolls.com
Civilization 4: Another great game and equally addictive. Released Dec 2005, it got a lot Game of the Year awards for the Overall and Turn-Based Strategy (TBS) categories.
www.2kgames.com/civ4/home.htm
All others pale in comparison IMO. Are there any others out there?