Lotus of Siam -- as good as everyone else says. Extraordinary. Service slow, but worth the wait. (We did dinner, so I can't comment on the lunch buffet.)
Lawry's -- expensive, and a very limited menu. But if you REALLY love prime rib, this is a place not to be missed. (Note that they do not have steaks or chops. Just Prime Rib, lobster tail and one fish entree.)
Lombardi's (in the Desert Passage shopping area of the new Aladin) -- really very nice and reasonably priced Italian food. the risotto was particularly good, as well as the chicken dishes.
The French Bistro (this may not be the correct name) at Paris Paris. We really enjoyed sitting outside and pretending we were in Paris. We really enjoyed the food. The waiter was obnoxious (he made it clear that he thought we were cheapskates for not wanting to pay for 'special' water, and when we shared a salad, it really upset him.) Nonetheless, I would return for the food and the setting. A good choice for a nice, but not inexpensive, lunch.