Kiroro. Pretty flat, gets a lot of snow which is great but without a decent pitch it can be hard to enjoy the pow. I had about 1m of fresh there one day ;-)
Asahidake, the stuff of legends, though Im not sure why. Worth a day, snowshoe to the sumit and ride down. Good experience, average riding.
Kamui. Never been there.
Teine. Steep. Easy sidecountry access. Lots of people on the weekend. If you get teine on a 30cm+ day its the best place in hokkaido IMO