OK - already going to Lotus of Siam. Would like to know the names of a few restaurants that are considered to be absolutely the best.

oh man -- so many!!! I can't afford the very top tier -- Alex, Joel Rubuchon, Picasso, but have greatly enjoyed Daniel Buloud at the Wynn, and most recently, David Burke at the Venetian.
Also, for a romantic dinner, Alize at the Palms is wonderful. Rosemary's is good if you want to make the 15 minute trip off strip.

I recommend ordering off the menu at Lotus of Siam. We went for the first time recently and loved the food. However, the lunch buffet looked pretty ordinary....IMHO

PS: We enjoy Diego's at MGM (mexican w/ a flair) & Mesa Grill at Ceasars (Bobby Flay's joint)

I've been very pleased with Joel Robuchon, Daniel Boulud, Mesa Grill and love Bouchon for breakfast!