What actually is a "mountain" course is a bit hard to define. For example, here in my area we have Country Club of the Rockies which is right at the base of a ski resort, however it is flat as a pancake. Is it a mountain course? Meanwhile, Red Sky has two courses literally built into the side of a mountain, with large elevation changes throughout. Vail Golf Club is dead flat except for a goat track up to a par 3 tee but is surrounded by 11,000-13,000 foot peaks closely on all sides. Is it a mountain course? Cordillera has 3 courses, the Summit, the Mountain, and the Valley, and all are laid over somewhat severe terrain.
Over in the Roaring Fork Valley (toward Aspen) the bulk of their courses are actually quite flat, and are more "river" courses in a sense than "mountain" courses.
Up toward Steamboat you have Haymaker which is actually quite dunesy/linksy in a sense, but has little overall vertical, while right next store you have Catamount which is one of the most severe sites I have seen. Most of the fairways could be blue ski runs!
Anyway, I'll submit that Frost Creek (I mentioned it in the other thread regarding unmentioned great courses) is the best in my area based on design/bones. Kind of a true mountain course on the front 9 but more of a river course on the back 9.