I've eaten at several metro Denver Indian restaurants, but the best so far was Masalaa - a vegetarian place in Aurora. The extensive menu offers everything from creative versions of such standards as vegetable korma (lightly flavored with a wonderful coconut/cilantro sauce) to about 11 different kinds of dosas. Also try the long list of iddly, uttappams, and the small but tasty selection of chaat (including a lovely dahi vada), and some of the best deserts I've ever had at an Indian restaurant (esp. the kulfi and the badam halwa).
I would love to hear about other quality Indian spots in Denver (or nearby), especially someplace that does decent chaat.