Best source:        North America  Top 10 by Snow Brains 

Other reference: North America Top 10 by Forbe: 

• Best: not high, but best "backcountry terrain"
• High speed up in 7 min (70 mph)
• 2,500 acres
• Vertical Drop: 4,140 ft

#2, Alta, Utah

• A lot beginner and intermediate runs (65%)
• Nearby big one: Snowbird
• 2,200 acres
• Vertical Drop: 2,020 ft

#3: Whistler Blackcomb, BC

• Best: size
• Vancouver airport
• A lot beginner and intermediate runs (75%)
• 8,170 acres
• 200 runs
• Vertical Drop: 5,354 ft

#4: Snowbird, Utah

• Best: tram
• Nearby big one: Alta
• 2,500 acres
• Vertical Drop: 3,240 ft

Town: There's not much nightlife, but there are enough good restaurants at Snowbird and its neighbor Alta to keep a five-day trip fresh.

#5: Alyeska, Alaska

• Not a good fit
• Very low height

#6: Revelstoke, B.C

• Best: vertical at 5,620
• 3,121 acres
• Trails: 59
• Lifts: 5
• Vertical Drop: 5,620 ft

#7: Big Sky, MT

• Best: the steeps
• 5,800 acres
• Trails: 299
• Lifts: 30
• Vertical Drop: 4,366 ft

#7: Vail, Colorado

• Denver airport, shuttle to Vail.
• Nearby big one: Beaver Creek
• 5,289 acres
• Vertical Drop: 3,450 ft

----

Colorado Ski Links:

1. http://www.familyskitrips.com/Pages/colorado_family_skiing.htm
2. http://travel.usnews.com/Vail_CO/When_To_Visit/
3. http://www.epicski.com/t/116073/is-mid-april-too-late-to-ski-in-utah-or-colorado-or-canada
4. https://answers.yahoo.com/question/index?qid=20101129184000AAhRvVT

Best Times to Visit Vail: Dec to Mar. In April, Vail in a state of sogginess. A little bit warm: 49 F in average in day time.

This user says the opposite: The best skiing in Colorado is in March/early