Rainbow Six isn't bad. Not really a Police simulator, though. I can't really name any like True Crime, since I think they saw how terrible it was and didn't make anything like it again. Until True Crime 2 NY, which I didn't touch.
TC 2 isn't too bad, it just gets really, really boring after a while and the story is pure shit. Rainbow Six is fine, too, it's just too much like "Let's go in there and kill terrorists" and not enough "Let's go in there and save lives", if you know what I mean. Not from a moral point of view, but just a gameplay one, since SWAT 4 has the latter kind of attitude and that's really appealing to me.