The concept at sleek Long Life is to offer a wide range of unfamiliar noodle dishes from China, Korea, Japan, and other Asian lands and serve them in a familiar Westernized setting (in this case, a super-modern space with lots of neon and Plexiglas). The problem is choosing from the 30 or so noodle dishes, all of which are wildly different. Do you go with Buddha's Bliss (ramen noodles in miso broth with smoked trout, tofu, and enoki mushrooms) or Enchanted Heat (a "Chinese hangover cure" composed of whole-wheat noodles, lily pods, tree ears, and secret healing ginseng herbs)? I recommend Ghengis' Buns, crisp sesame biscuits filled with Chinese roast beef, cucumber, cilantro, and hoisin sauce. Wash it all down with Cool Cucumber Juice or Ginseng Ginger Ale. Another branch is in the Metreon food court (101 Fourth St.; tel. 415/369-6188).