It depends on what the models are being used for.
Half-Life 2 for example most of the models are:
2,500 (low) 4,000 (med) 6,500 (high) for the character models, and just think of how many are on-screen at once.
All of those characters have 256x256 (low) 512x512 (med) 1024x1024 (high) diffuse/specular/normal textures. The PC just has far more space for that sort of thing, because to use the high settings for both you're going to have a Shader 1.1 Card with 128MB dedicated VRAM at least.
Depending on the console you're using it depends on what the model will best have on it.
PS2 for example only has 4MB VRAM so utilising more polygons is far better as while it can't use shaders, or textures to improve graphical quality; you can have almost 4x the polycount on the models than you can on the xbox or ngc. Killzone makes a good example having 12,000 polygon models with per-vertex lighting but 128x128 4bit textures. The overall quality end up being very similar to Half-Life 2 which uses much better technology.
This said when you have less on the screen like you have with fighting games, much more can go on characters and environments than an FPS where you have legions of characters coming at you.
Some use polygons for a style purpose, like Sonic. It hardly pushes the performance of either PS3 or Xbox360; but people are now used to how Sonic looks, so they just seem to upgrade the polycounts a little then spend more time on graphical effects.
It's down to what the development team are willing to push for the sake of the game itself. Halo 2 for example has fairly low-polygon models in comparison to other games, like Unreal Championship 2..
Halo 2 generally has ~3,500 per model
Unreal Championship 2 has ~6,500 per model
This said there is a huge difference in how the visual weapons are done, effects and environments. Both games push the Xbox to it's absolute limits and look gorgeous.
Bet this post was made for someone who wants to see what polycounts they can get in to DBPro or something; but really when developing artwork for games people need to learn to create an engine and stress test what it is capable of on the hardware they want to use as the minimum specifications.
Intel Core 2 Duo E6400, 512MB DDR2 667MHz, ATi Radeon X1900 XT 256MB PCI-E, Windows Vista Business / XP Professional SP2
