Steak houses at the Grand Sierra, Harrah's and the Peppermill are excellent. I really like the steak house at the Western Village in Sparks. It is a great dining experience.
If you like seafood, I recommend the oyster bars at the Silver Legacy, Sparks Nugget and the Atlantis. The Atlantis has some great sushi.
If you like italian, I recommend La Strada at the Eldorado. A couple of good italian restaurants outside the casinos are Johnny's and La Cucina.
If you want meat/ribs, there's a casual place downtown called Men Wielding Fire.
And finally, if you want the best burger in the western United States, go to the Nugget in downtown Reno. It is the home of the original Awful Awful.