Mammoth and Squaw are my two favorites of all the places I've ridden, by far. Thanksgiving at Mammoth this year was ridiculous. Based on what I've heard, I expect kirkwood to fall into this category if I can ever get down there. My second tier consists of baker, telluride, and crested butte.
Other stuff I've ridden to give you a point of reference:
vail - almost in my 2nd tier. i was only there for 1 day...and it wasn't a great day
loveland - weird, decent
keystone - nice park, decent
eldora - quaint, charming, small, boring
stevens pass - small, decent park, fun at night
homewood - literally ON the lake. kinda cool, but small and just decent other than that.
Friends of mine seem to like sugar and northstar, also...