I live in Laax. The top 5 of where I have been (after skiing most of Switzerland, France, Austria, Italy, Utah, Colorado, NZ, Argentina):
Breckenridge
Keystone
Buttermilk
Snowmass
Park City
I have never been in Whistler or Mammoth.
Those top lists from mysnowparks.com are useless as they represent peoples home mountain, they are not based on people who have actually traveled around the world / europe and have seen the difference with their own eyes.
European parks just don't compare. Laax and Schnalstal are the only ones that get very close to American standards. Parks like Val d'Isere, Avoriaz, Mayrhofen, Les 2 Alpes are a lot of fun, but they are a total mess. Shaping in most Colorado resorts is done to PERFECTION, every day of the season, and incredibly consistent. The only place that is equally consistent in Europe is Laax, but Laax is still lacking in terms of the layout/length of the lines and how the pipe is shaped (there is no direct snowmaking on the pipe).
Snowpark NZ is comparable to Laax in my opinion, super consistent but no sick lines like Breckenridge or Buttermilk.