I agree, Dirt is my favourite of the three because while the physics aren't great, they're not great in 2 or 3 either. Stages are narrow (I can't remember the length), unlike Dirt 3's, there's a lot of variety in the cars (big rigs and raid trucks are great fun) and Pikes Peak is in there, albeit split into a few separate stages (might only be two, might be more). Dirt is the one I keep coming back to every few months to put some more progression into the career, Dirt 3 lost me after I realised I'd never complete the career properly without buying the DLC. I always forget I have Dirt 2, though, because I don't have it on Steam.
WRC 4 is great though, I haven't tried 3 or 4 with a pad on PS3 but I'm pretty sure I heard 4 was improved in that respect. It doesn't have the Group B or historic cars that WRC 3 had, however.