Tell us a bit more. What kind of skiing do you like, skill level, apres interests, budget, travel needs, etc.
One all around champ I like is Snowmass, but many others might work even better for your specific interests.
Totally depends on what you are after. If you want glitz and glam and lots of stuff besides skiing to do, then Colorado is the place to go. If you want true great skiing with not as many ammenities then I recommend Jackson or Big Sky.
Doesn't matter. North America in Jan/Feb is about as good as it gets everywhere. See one of thousand other threads on here with vacation recommendations. You should ask questions like, "Can you recommend a resort with lots of steeps and a good ski school", or "Can you recommend a cool mountain town", etc.