If the Rio were actually on the Strip, it would be my choice every single time. The rooms are all suites and super clean. They feature some great restaurants, including one of the best wine bars in Las Vegas, both on the Strip and off of it.
The buffet, if that's your scene (it's not mine) has some of the best food...though you must visit the seafood buffet, not the regular carnival buffet.
Their Lounge, Voodoo, is one of my favorite after hours spots, located on the top floor/roof of the hotel. The ride up is amazing, with clear elevators that take you all the way up!!! The drinks at Voodoo are a bit over priced, but the flare bartenders and the size of most of their drinks are worth the extra price!!!