I've skied all of the mountains you listed except for Telluride, and I ski Vail on a regular basis so, here is my humble opinion.
Vail is awesome. Whoever says it is flat doesn't know where to look. Vail has more inbounds cliffs than any other 5 mountain resort (my home mountains). The bowl skiing can't be beat, and there is steep stuff in Sun Up Bowl, Sun Down Bowl, and all over Bluesky Basin. Vail is also many times the size of Alta and CB, and you couldn't possibly ski it all in one trip.
Crested Butte has some absolutely insane terrain. The north face area is where the US EXtremes are held, and there are some ridiculously steep lines over 50 degrees with unavoidable drops that are sometimes in the range of 20-40 feet (look up Body Bag if you go there just to see what I am talking about). Great skiing at CB.
Alta is a skiing mecca. Every skier should go there at least once. It gets about twice the snow of any of the Colorado mountains, and the average steepness trumps just about any Colorado resort. Alta and Snowbird (they are connected at the top) are the only two places in Utah that I hold on a higher level than the best of what Colorado has to offer.
I've never skied Telluride, so I don't have much of an opinion. I would think that Alta and CB are a little bit better for steeps.
I guess it comes down to this- How many days are you going to be skiing, and honestly, how good are you at skiing steep lines? If you aren't amazing, you aren't going to be able to ski the harder stuff at CB. There is stuff there that Seth Morrison has backed down from because the conditions weren't perfect. If you are ok and can handle yourself on an average rocky mountain double black, go to Atla. If you get bored at Alta, you can hop the ridge and ski Snowbird. If you are going for a really long time though, I would say hit up Vail because it is so big and won't get old, and if you want a change you can head over to any other 5 mountain resort and use your Vail lift ticket there.