for your own portfolio (and since most of us don't have a game engine handy) you can usually just apply that stuff in Maya.

As for polycounts, they're pretty dependant on the game itself. It's also a tad difficult to really guage a model's actual polycount because of the advancements in normal map and parallax map technology. I'd be willing to estimate that 10,000-15,000 polys would be around the max for a non-fighting game (as in, a game that would have more than two characters running around at a time).

But even still, most games give the main player character a higher polycount than the bad guys. So, while a next-gen Lara Croft could probably be 15,000 polys or more (half of that in the boobs, I'm sure ), the enemies she faces are probably closer to 8,000... that kind of thing.

I'd be willing to bet that just because of the sheer number of characters on the screen at once in games like Call of Duty 2, that they are more in the 5-8k range. Although I'm sure they use some nice LOD (level of detail) models so that the closer they are to you, the higher poly they are.

Be careful when you read things about "millions of polygons" for a character or something, as what that actually means is that the normal map was generated from a very high res mesh (probably in zbrush) while the actual model that runs around in the game is much (much) lower, as described above.

For a portfolio, I'd recomend having lots of different ranges of polycounts in your work, from 1500 poly characters all the way up to the 30k or whatever, not just to show you can work with multiple restrictions, but also to show you could make different LOD versions of a model.