P.S. best Mexican and Chinese...what's your fav?
Las Vegas has been fortunate in having had a plethora of Mexican restaurants open over the past few years, and in truth some of the most interesting are the little "mom and pop" places that specialize in a particular dish or region. But for my money the gold standard continues to be Los Molcajetes, at 1553 North Eastern (http://losmolcajeteslv.com/). An old Chowhound thread can be found here - http://chowhound.chow.com/topics/605914.
Narrowing down Chinese is not so easy - we are loaded with places in the "average to slightly above" range, but not many true standouts. It may come down to which particular cuisine you are looking for.
Juan's Flaming Fajitas and Cantina is a New Mexican restaurant that is very good. It is on West Tropicana west of Fort Apache in the same center as In n Out. It is in the same spot where Buzz BBQ use to be. About seventy percent of the staff use to work at Viva Mercados before it went out of business.