Pretty much all the mountains in Montana have something going for them. Big Mountain has kick ass tree skiing and pretty consistent snowfall, Big Sky is huge and you can ski most of the mountain at 50mph if you feel like it, and Bridger has crazy technical terrain. I'd shy away from recommending Bridger unless you have a beacon, are willing to hike, and are going with a local, though.
And I'll be the first to recommend going a bit south and doing the Jackson/Targhee thing. A day at Jackson is expensive, but totally worth it, and Targhee is one of the coolest little mountains I have skied. If you have backcountry gear, the pass and the park would be worth it even if you totally avoid the resorts.