Count me a fan of any and all good tacos.
I like the style of taco that's probably the most common in taquerias: two tortillas topped with a meat and garnished with cilantro, onion, and/or radish (with salsa and lime wedges on the side). (This is a taco de cecina from Juanita's in Dallas.)
...be aware that the reason most taquerias double up the tortillas is that they're using thin, manufactured tortillas that tear and leak easily. When you have thick, freshly made tortillas (such as the ones pictured above with lamb barbacoa at Dallas's Barbacoa Estilo Hidalgo), only one tortilla is necessary. (If your local taqueria doesn't serve freshly made tortillas, consider scouting around a bit more. A taqueria that cares enough to make fresh tortillas is more likely to care about the quality of other things as well, and vice versa.)
Americanized crispy tacos (such as the awful one above, at Ojeda's in Dallas) fall into a few common traps. First, they often resort to preformed taco shells. Second, they often use poor, mealy ground beef with generic seasoning. There's nothing un-Mexican about ground beef. Carne molido and picadillo are fairly common as fillings in Mexico. But they usually have (a) better texture than American ground beef taco fillings and (b) a much more interesting flavor profile (often incorporating other ingredients, such as potato, nuts, dried fruit, et al.). Third, Americanized crispy tacos are usually heaped with low-grade filler--bland iceberg lettuce, unripe tomato, and poor cheese. There are, however, some places that steer clear of such problems and have excellent crispy tacos. They're few and far between, but well worth tracking down.
And don't forget the San Antonio-style "puffy taco" (such as these, from Henry's in SA).
And then there are tacos de canasta, tacos dorados (the Mexican progenitor of the Americanized crispy taco), and probably dozens of other types across Mexico.
A good taco is a good taco, regardless of the style or tradition. And "authenticity" (which is hard to get a handle on anyway) is no substitute for great taste.