When are you going . . . because The Lion King is opening in May at Mandalay Bay.
If you're into magic, Lance Burton's show at Monte Carlo is pretty good.
The new guy at The Mirage, Terry Fator, is getting a lot of really good buzz. He won one of the TV shows (America's Got Talent) and some people at my office who saw him REALLY liked him. He replaced Danny Gans, who moved over to the new Encore Resort.
Donny & Marie at The Flamingo is selling out over & over.
Bette Midler's show is really good; she is at Caesars.
Jersey Boys is at The Venetian/Palazzo Resort; I saw it in New York and it is supposed to be the same production.
Blue Man Group is also at The Venetian; my kids really like it.
If you want something more adult, the Crazy Horse show at MGM Grand is something very different. The Fantasy show at Luxor is also supposed to be very sexy; their lead singer, Stephanie Jordan, gets a lot of good press.
Have fun planning your trip!