I've had a big challenge finding pizza in Vegas worth coming back to, until I came to Rosati's. The style is Chicago deep dish and they do a pretty good job of replicating it. My friend and I split a large for about $18 and we had plenty of left overs for the next day.
The cool thing here is the dining area having self-service drinks so you never go thirsty. As with any normal Chicago style place, the pizza takes a long time to cook, but it is well worth the wait. A normal person will be full after one or two slices, but it was so good I had about 4 or 5... Whoops!