No, it's not. While subsurf(by the way, you should keep your fingers off of that unless you know what you're really doing) adds more polys to make a model look more smooth.
The equivalent is soft and hard edges
You set them hard/soft in the editing panel(press F9) right under the material section(set smooth/set solid). Note the 'AutoSmooth' function top right, in the next panel.
@Soil: Thanks from me too! I confused the terms. Just started with blender and learned about subsurf, I thought «wow», I can help someone, but well, too bad.
@Leopardo: Actually it shouldn't make blender crash, maybe you set the number too high and your hardware couldn't handle it?
I read that you shouldn't really set it higher than 2 - 4 or something. Now I will be careful with that too, because it can make the program crash. Hope you saved your work before!
just for reference, 4000 triangles subdivided 6x is 16.3 million triangles....even subdivided 1x its 16000 triangles.
I dont think sub-d's have any use in videogames right now...but voxel octree's look promising, but thats wayyyyy off topic.
Guesses it wouldn't be useful for game models though the subsurf makes it easier. At the moment I try to get a grip on modeling itself and later on going to low poly game models. To keep it offtopic: Barf, I really like your new face models. I hope you are still working on it!