I go often. I have stayed in the following and would rank them in this order:
Venetian, Palazzo, Wynn, Bellagio, hotel at Mandalay, Caesars (Augustus tower only for this ranking), MGM, Mandalay Bay, New York New York, Monte Carlo, Mirage, Treasure Island, Paris, Luxor. I would not stay at the Paris or Luxor again.
I have seen the following shows and would rank them: Beatles Love Cirque, Ka Cirque, O Cirque, Celine Dion, Le Reve (Cirque-like but doesn't have the Cirque trademark name), Mystere Cirque, Zumanity Cirque, Phantom of the Opera. Watch for visiting variety/comedy shows too; there are many great performers who have temporary shows there and we've seen a ton of those that are great. If you want to see any of the Cirque shows, sign up at the Cirque website and they offer random discounts and you might be able to get one for the time of your stay.
Sign up on the various casino websites and you will get sent room discounts. Watch prices because a big convention in town will signficantly change those rates; it's better to switch your vacation days and get lower rates. I went last month and stayed at the Wynn for under $500 for 3 nights and I had a $100 food credit and we used it for a complimentary room service breakfast one morning.