Wynn Encore is my favorite for a 5 star. Rooms are very nice and the pool is awesome and never that busy but its a little bit out of the way.
Aria and Cosmo are my go to as the location, price and quality are tough to beat.
Another interesting option if you don't gamble is the four seasons. they don't have a casino is its a lot quicker to get out and they have a bunch of house cars (A7's) that they will drive you to other places on the strip. The food choices there are fantastic. Charlie Palmer Steak House is amazing and normally has an awesome deal called the cut of the week. it changes weekly but includes bottomless wine pairing for around 50 something a person.