I used to love both Cafe Rio and Barbacoa when I lived in SLC - left in 2011. Qdoba is pretty good, and probably my favorite up here for that type of Mexican food - altho Baja Fresh is pretty good.
In my opinion, there's 5 different types of Mexican restaurants.
There's your crappy fast food barely call it Mexican, like Taco Bell or Del Taco or Taco Time. They have their place, but they're certainly not GOOD.
There's taqueria style, which are almost never chain restaurants, except for maybe Rubios? Maybe a place has 2 or 3 locations. They're always super greasy and super delicious.
There's the "fresh Mex" style, which is what we're discussing here. They at least FEEL healthier than taquerias, even if they're not.
There's basic sit-down Mexican places. These are fairly interchangeable - some of them are better than others, but they all serve the basics and fill you up really well.
And then there's super authentic, like Red Iguana. These are pretty rare, but the absolute best.