Tastes like mileage may vary.
But it isn't a yardstick measurement. New Mexican food is its own animal, and in some cases, is very different from American Mexican. It's a mix of traditional Mexican and American Indian meals. It is also, I might add, the oldest food-form in the United States. Any "Tex-Mex" (or whatever) style of food is really a watered down derivative.
Take carne asada, for instance. In New Mexico cooking, the beef is soaked (usually while still on the bone) in red chile and tequila for (up to) several days. In Tex-Mex cooking it is usually just low quality steaks marinaded in cumin, chili powder, garlic, olive oil, and usually water.
With pretty much anything, you're likely to see drastic differences in quality of meats, the preparation, the spices used, and the like. But there is the one significant difference that
Mallory,
JustKate, and I keep repeating here: the green chile.
I've been to several places in both Texas and Arizona where they don't even have it. And even with the ones that do, it's usually just chilies from a can. You're certainly not going to see fresh (often roasted) Hatch New Mexican Chilies at any of these places which is pretty much a mandatory staple.
Another thing you won't see anywhere outside New Mexico is a good Sopapilla. But that's a horse of a different color.
I wouldn't say it's not as good, it's just a different type of Mexican food. Tex-Mex, which is what a lot of Americans think of a just "Mexican", is awesome in Texas. New Mexico has it's own type of awesome style of Mexican food as well. And in Mexico itself, there are multitudes of different type of food, many of which is very different than what we would think of as Mexican food.
Though I'm more partial to the Tex-Mex style (and think we do it best

), I love all types of
la comida mexicana!
Well, I've worked in both types of restaurants. And between knowing what I know now and just the difference in taste, the "Tex-Mex" just doesn't do it for me.
That's not to say New Mexico doesn't have its fair share of Gringo eateries. It's just, most of them are in Santa Fe and are meant for tourists. I never eat at them.