10k tirs is the middle limit the standard.
Depends on the game MMORPG requires less due to lot's of details like for example WoW.
On the other hand i have a look @ diablo III models they are REALLY HYPER DUPER LOW POLY .... but i don't know how with textures and other stuffs they look very real and the isometric camera do the job. So it depends.
Why are you asking my friend are you going for a game ?