(Could care less about apres ski or tree skiing!)
Sorry, I misread the title. I thought it was Canada only. Being that I like long steep vertical runs (and a bit of tree skiing if they're not too tight) I vote (with a close margin between the three):
Mont Ste Anne
Out of the other places I'll vote a 2nd tier that is behind the first tier by a fair bit, but relatively close with each other
Blue Mountain (Ontario)
Mt St Saveur
Mount St Louis
Silly poll because tree skiing is what makes the best resorts in the east the best resorts in the east.
Without tree skiing, I'd knock off Jay.
Stowe definitely belongs in the top 3.
Heard good things about Sugarbush, Sugarloaf and MRG, but never been. Killington would probably be a good choice for sheer size.