Tacos in NYC are like pizza, in that everyone's favorite taco is the one they grew up with, the one they probably got just down the street from home. A little tip: it's authentic if you can find Guadalupe somewhere on the premises.
Though I certainly have not tried all the taco joints in the city, I do have two favorites. And the third I'll include in this post is Jennie's favorite.
So first, the Empellon guys. I've been to Empellon Taqueria in the West Village and Empellon Cocina in LES.
I love them both. The former introduced me to queso fundido (melted cheese with various mix-ins that you eat on chips or tortillas) and dog fish. The latter introduced me to goat tacos and this awesome uni creation.
However, no matter how many tacos I've tasted I still keep going back to my local taco truck, Taco Rey de Oro, located under the 7 train on the 52nd street Lincoln Ave stop. I've gone there for years, and they have THE BEST lengua quesadillas EVER!!!
Not everyone serves lengua, which literally means "tongue" and is usually beef tongue. Before you get all grossed out, I want to tell you that it's a delicacy, and when made right is so nice and tender. Plus it has that fatty taste without being fat. Can't get any better than that.
Then there's Jennie's favorite, Zaragosa Grocery, a little bodega near Stuy Town in LES. The guy has tacos, quesadillas, tamales, chips and guac, everything.
In sum, authenticity definitely wins. Best about all these places: they're all cheap. Good food on a budget FTW!
Final note: I can be as stubborn as Californians with their In and Out when I say Taco Rey de Oro is the best. I'd be lost without them.