Face count completely depends on what type of game it is. DOA3 and RE reserve most of the polys for the characters. In other games, the environment and craft play bigger roles.
IMHO, forget about building a low poly character. Just build a character, put everything in there. 10K or 50K. Whatever it takes. Model the wrinkles on the clothes, model the facial structure, as many triangles as you want. No arbitrary global smoothing cheats, tho. Make those triangles count (cos they still count!).
Then concentrate on effectively downrezing the same model to as low as you can get away with and still be animatable. Do a bunch of versions. If your app allows, put several different rezes into an LOD group from your highest to - heck, even 300 tris and test it out.
The trick is to do it cleanly. Start thinking more along the lines of FMV control meshes and sub-dsurface modeling techniques.