I, too, love the Tohoku area for skiing.
But Hokkaido is really the scape up. Niseko is not at all at high altitude - as a matter of fact, the bottom of the slopes are more or less at sea level, and you can see the sea from two sides of the ski field. But the snow is simply amazing.
Furano has a good reputation, although I never skied there. The main interest of Niseko is the easy bus access from Sapporo airport, a good choice of onsen and many runs to choose from