I can't have a favorite because I've played all of them for long periods of time and I got used with all of the different environments and handlings, I played Trackmania Original, Sunrise, Nations ESWC, United, United Forever (no nations forever here because when you own United forever you automaticly have nations forever as well) then to Trackmania 2 Canyon, Valley and Stadium.
Yup, not a fan at all. /sarcasm
You know what, we should make a Trackmania Megathread.