Polycounts depends on 3 things...
a. target system specs
b. how many instance will be onscreen at once
c. object effects (suchas Textured, Shaders, Texture Blends, etc...)
Unreal Tournament has models that are 2,500 polygons each, they also have LOD (Level of Detail) models for the further away the less detail is required and as such doesn't need to process the same number of polygons.
However Unreal Tournament levels are around 90-150,000 polygons onscreen at a time...
Resident Evil Zero / Final Fantasy where it is almost purely the game models showing, you can actually push them into 10,000 each without the graphics card flinching.
Things to remember...
single mesh models are better for animating, however when you have large numbers of polygons (1,024+) in your model, try to split them up into seperate mesh as single mesh 2,500 polygon models are slower than a model 2,500 with 5x limb that are 500polygons each.
Textured models are around half as fast as non-textured.
Shadered models will require more speed the more vertices you have in your model (not the more polygons).
Lastly, games do no measure polygon count in terms of what each model can be... you measure it in how many polygons/vertices your engine can push per second.
If you take that and divide it by 60 (for 60fps) you will get the MAXIMUM you can have, but i would always aim for half your maximum.
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