From a discussion in which several very smart people were saying, "I get that I'm supposed to like Touch of Evil, but what's the big deal?," my response:

Why Touch of Evil is a good (& great) movie:

1) The opening tracking shot. The bomb is introduced (on the side of the screen, too, so pay attention, kids), throwing the plot into motion. As Heston & Leigh walk towards the border, discussing their marraige (and establishing most of what you need to know about them), the doomed car matches them step for step, building the tension (will they kill Heston & Leigh in the first shot of the movie? Hey, that's not a bad idea -- someone call Hitchcock.). You can almost miss the floozie complaining about the ticking noise in her head just before the car finally shoots forward - just beyond where it will kill Heston, Leigh, and a bunch of other innocent people, and explodes. Then the car explodes (in bad film stock, too, just like they would in any regular drive-in movie). Then, in a few minutes, Quinlan appears, all of that mass sliding out of the car behind that squinting, bulbous, evil, messy face like a caricature of malevalence.

2) Janet Leigh's first interaction with Uncle Joe, with the way that her 50s-fluff attitude suddenly meets a guy who's mean in a way that few noir movies could really convey. Uncle Joe & his group are out of time; Leigh is sure that she can't be hurt because, after all, she's white, middle-class, and American, not to mention married to a cop. Uncle Joe carries enough real menace to let her know that she's not in that movie anymore; in fact, no one is.

3) ToE's Tijuana, which is lit in such a way that it seems all giant facades and pitch-black alleys, like one of those nightmare paintings (what was that artist's name?) of the super-creepy dusky town squares. The movie lays claim to Tijuana as dreamspace, reality through the mirror, just as Mexico plays the part of America's Id throughout the movie. (Vargas: "This isn't the real Mexico. You know that. All border towns bring out the worst in a country.") Welles figures out how to have his cake & eat it, too, because the movie specifically plays off of the expectation that most of its viewers are going to hold racist opinions about Mexicans, and it pushes those buttons expertly. Whenever anyone from Uncle Joe's gang appears, they are the Mexicans To Fear, full of attitude and violence. But the movie nonetheless goes on to show that the crimes of Uncle Joe's gang are just run-of-the-mill crimes. It's the American sheriff -- the racist white ranch-owner -- Quinlan whose crimes are much more serious. (Vargas to Quinlan: "A policeman's job is only easy in a police state.")

4) The questioning of the suspect. The movie so directly subverts the audience's expectations that I couldn't even see it the first time. The confession, the evidence-planting, the proof of guilt -- it all takes place off-screen. The camera keeps shifting to a different room, following Vargas as he realizes what's really going on, that Quinlan's planting evidence. Who cares whether the kid did it? The ostensible plot A part of the movie is completely beside the real point.

5) Janet Leigh at the motel. Yeeks. Yeah, on one level, it's cheese. On another, it's the most nightmarish part of a nightmarish movie. Dennis Weaver's skittering hotel clerk is the worst-possible bystander, afraid to help & denying his responsibility. Welles puts Leigh in the most uncomfortable situation he could -- she's alone, constantly being leered at by Weaver, then Uncle Joe's guys show up & terrorize her before they drug her and possibly gang-rape her. When the girl whispers to her through the wall about what's coming, it's both hilarious (Reefer? Really?) and unsettling (why is she whispering? Where is the rest of the gang? Doesn't the whisperer come with the rest of the gang to hold her down & drug her?). Urgh.

6) The final scene. Quinlan is confronted with his crimes by his sidekick Menzies, and the crimes are, like I said, worse than Uncle Joe's, because Quinlan's crimes are against himself and his friend's trust, as well as justice itself. Although it makes no technological sense that Vargas should have to scuffle along to listen in, it makes perfect emotional sense. After all, Heston's been scuffling along the edge of this movie the whole time, trying to figure out what makes Quinlan tick. This is all taking place in Tijuana, too, which is Id-land, where nightmare logic works. The industrial site that Vargas creeps through looks like something out of Bosch, and Vargas hasn't kept his hands clean -- he's currently having a loyal friend betray another, while ignoring/avoiding his wife in his quest to be right. It's only when Quinlan & Menzies (and Vargas) cross back into America that they leave the dream logic & get to the really dirty stuff. Quinlan realizes that his friend is wearing a wire and shoots his best friend/sidekick, then wanders down to the filthy river to clean the blood off his hands (and to try to kill Vargas). He's shot instead, and Marlene Dietrich, the only other person (than the man who he's just killed) who loved him, is left to pronounce his epitaph: "He was some kind of man. What does it matter what you say about people?" Damn straight. Quinlan's more of a man than a monster, and the movie is powerful enough to show that Quinlan deserves the audience's sympathy as much as its contempt.