NFSU if you can take the "Holy fuck I want to bust my controller out of anger" levels it gives you.
NFS3 for coolness (Hot Persuit 2 was *ok*)
ANY of the carmageddon series if you are not totally into racing, but still wanna have a bash all fun time
and for realism, GT2 as previously stated. That game wasted more of my life then any other racing game COMBINED.
For me, its not about pretty graphics, but sheer quality.