Not even necessarily for people on the lower edge of the spec. Games are often optimised for the settings they're expected to use. For example, take Quake 1 - my computer is RIDICULOUSLY over spec for that (I guess most peoples are!) but if I load in a couple of 700+ poly models it runs like a one legged dog. The game simply wasn't designed for models with more than a few hundred polys, usually less.
Now, Quake3 - a few models like that is no problem. The point is, as well as your PC being able to handle it, so has the game engine.