[Qore]

As an avid MMO/MMORPG player I recommend the following games:

MMORPG:
TERA - Amazing take on MMORPG gaming with a unique combat system
Lineage 2 - Played this for 8-9 years. TERA's development team was originally L2's dev team, many similarities, more of a traditional MMORPG, great graphics.

MMO/MOBA:
DoTA 2
League of Legends
Team Fortress 2
Counterstrike: Source - Global Offense is just a retexture of CSS. Plus I prefer older graphics
Garry's Mod - Plenty of things to do and explore.

Downloading TERA now. It looks beautiful, and from what I read, it's very detailed.