Niseko is the most well known Japanese resort with international visitors, and with good reason - it's an absolute powder playground. It offers endless deep, dry snow - as much as 15m per season; and the terrain to do it justice.
The ski area is comprised of three sectors- Grand Hirafu (Hirafu and Hanazono), Annupuri and Higashiyama. The three are linked, but not as efficiently as you might wish. There are modern lifts, but also some old single chairs on upper slopes. The snow often falls almost constantly from December to the end of February, potentially refreshing the slopes almost hourly, although this does mean there are very few fine weather days.
There are several modern ski-in/ski-out hotels (but little else) at the bases. Or you can stay in the atmospheric little town of Hirafu where, in the last few years, impressive modern apartments have gone up beside traditional pensions and lodges. One thing to bear in mind is that Niseko is not the best choice for those looking to experience Japanese culture - it has a very international feel, with all the pros and cons that come as part of that.