I spent 21 years in New Mexico, and have been in Georgia for 24. I also lived for awhile in Oklahoma, Colorado, Kansas, and Missouri and have travelled in 44 of our 50 states, as well as 5 Mexican states.
I have found excellent Mexican food all over, as well as terrible Mexican food all over. What I enjoy most is a well prepared meal - or. at least, a well prepared dish.
A green chile cheeseburger in New Mexico is hard to beat. Fresh piping hot sopaipillas in New Mexico are about the best bread I have ever had. The tortas and burritos in some of the Mexican groceries and taquerias in Georgia are absolutely delicious. The Tex-Mex food offered in several local mini-chains is generally quite good.
This past Friday evening, we tried a Mexican place near where we live. It has been open about a year, but we had never been there. We were not excited to see the "Restaurant For Sale" sign in the window - but we went in anyway. This sit down restaurant appeared to be geared toward the immigrant community. The Spanish language tv program was on so loud that my wife and I could not communicate. I ordered a dish that I saw being delivered to a nearby table. I don't know the name of it, but it was very enjoyable. I had five reddish corn tortillas filled with lettuce, tomato, and avocado. Beside them was a quantity of grilled chicken strips such as would be included with a fajita plate. Additionally, the plate had beans, rice, and lettuce with tomato.
To answer the original question - I think, at the moment, my favorite is the hole-in-the-wall place here in Georgia which is geared to the Mexican nationals who live and work in the area. Several places I have discovered are very good - and very reasonably priced. That is a great combination.