I agree that it depends a lot on conditions. But a few general notes...
Telluride: I think they're trail rating is pretty much spot-on (although I am likely biased as this is where I learned to ski and is still my all-time favorite resort). I love that they have 6 different trail ratings, and I've found a great gradation in challenge matching their listings.
Arizona Snowbowl: some of the greens and blues here seem to be more difficult than at many other places I've been. But their single black diamond runs seem average or easier-than-average.
Brian Head: what I experienced was definitely on the easy side, but they also had one lift closed all day and I only got one ride up Giant Steps before the wind closed it, too. But every run I took was easy for its markings.
Timberline, Oregon: Also seemed to trend easy, although they did have short but fairly steep chicken hills in a few spots, even on easier runs.
Mountain High: a wacky mish-mash--they seem to have kept the trail ratings from each of the three precursor areas without any real attempt to standardize them. So now... MH West (the old Blue Ridge) has easier-than-usual trail ratings. Vertigo, their steepest regularly-opened run is marked double diamond (and therefore usually empty even on the busiest days), but I can ski it pretty easily in all sorts of conditions--and if I can do it, that means it's definitely not very "extreme"! MH East (the old Holiday Hill) seems a lot more difficult. The blues and single blacks on the main face seem to compare to Vertigo in difficulty, while the double-blacks are too scary for me. The beginner runs up top also seem more challenging than those at West (and I haven't tried First Tracks at the bottom). MH North (the old Ski Sunrise) is just different... the pitch seems consistent with beginner terrain, but there are a couple steeper sections and the trails are much narrower than at the other two areas, adding another dimension of challenge.
Snowbasin: More challenging--their blues seem plenty challenging for me.