It isn't my kind of game either, just thought it looked nice.
I think the point of it is, the stuff like the animated crowds, water tesselation and the lighting imo looks incredible and I don't see how dx9/10 will have those features.
My nephew already has it for his Xbox (or PS3 I get confused
) so as far as I'm concerned it's a bit of a port and thus is poopy, Alien Vs Predator whilst still being a revisited title holds a bit more promise though. But if people are getting off on Dirt2, then good luck to them I say.