Tough question I know, but if you had to pick one ski resort, what's your favorite and why?

I'm going to hedge on my own question and pick 2.
In North America I'm going with Whistler because of its size and large number of great intermediate cruising runs. The Peak to Creek run drops 5000 ft and is just one of many great runs.

In Europe, I have to go with Zermatt. Great runs but its also a great village with absolutely fantastic scenery. Being able to ski 2 countries (Switerzland/Italy) is really cool.

My favorite, based on where I know that I'll always have a good ski day starting with the blue cruiser run Mozaart, is Keystone. And the restaurant Apenglow Stube simply cannot be beat (although the gondola ride down after dinner will wake one up from the warm relaxed state usually following an exceptional meal).

In Europe my favorite is St. Anton based largely on the atmosphere and the better slope grooming compared to the other Austrian ski hills we visited (which admittedly was a snapshot visit).

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"[F]ollow your bliss and don't be afraid, and doors will open where you didn't know they were going to be." Joseph Campbell

I would say that Park City Utah is my favorite place to ski. Although, I have not skiid there for a long time there have probably been a lot of changes. I like the snow in Utah better than anywhere else I have been. I like the way the resort is laid out and the service and the facilities are great. It is also reletivley easy to travel to.

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Love to ski

Whistler.
It's huge and it has A LOT of variety. Despite the 5000ft vertical drop, the bad thing about Whistler is, below a certain elevation (about half way I believe) often it goes above freezing and so the snow turns really watery and thick. Otherwise the snow is really fluffy.

Park City was also nice. IIRC, I went with a college group the year of the '02 winter olympics. I recall seeing bunch of olympic runs and such..