In the Sawatch, basically any route that isn't the standard route will be fine and you'll hardly see anyone. There are a few exceptions (Holy Cross comes to mind).
I've climbed Yale, Princeton, and Missouri on weekends via alternate routes and seen almost no one on any of them.
My faves in the Sawatch:
Grouse Canyon on Princeton -- 1000 times better than the standard route (which may be the worst standard route on a 14er other than Bross). Chest high flowers and nice waterfalls. (Click photo for larger version)

Brown's Lake for either Antero or Shav/Tab -- I backpacked in, which was nice
Missouri via Clohesy Lake -- I saw no one at all on this route (2005) and I saw beautiful Columbines all over the place.
Yale via the east ridge (there are two routes to access it) -- I saw no one until the summit
There are some alternates on the easier San Juan Peaks as well, but once you start getting into the harder peaks the number of route choices drops and you see fewer people anyway.
I'd also like to put up a vote for Snowmass Mountain's east slopes. Yes, it's the traditional standard route but these days the west slopes have essentially become the standard route, probably because of a combination of people wanting a shorter trip and it having been the only route on this site for a long time. This has happened despite the fact that the west slopes are a miserable choss heap. The east slope is a beautiful route with a nice snowclimb and a beautiful lake to camp at. And in the middle of last summer on a weekend we were the only party to climb it from that side while 3 or 4 struggled up the west slopes.