Joker was very popular as a meme, and the characters itself is fairly funny. There's some self-awareness in it, and it seems to have carried across to the meme, with shitloads of people posting the character somewhat ironically. Kind of like that bit of art by hladilnik, with his opossum character in Joker make-up, which someone liked to post in the thread. The character is a slightly edgy/crazy nerd, so you're like "oh, it fits, that's kinda funny".
The same is not true for the guy for No Country for Old Men. He's played 100% straight, and everyone I've seen who praises the movie, character, and the actor playing him eats it up. They think the whole act with the coin and the cattle-killing device is menacing instead of edgy. I've been told the point of the movie is that there is no place for old style heroes in modern film, and that just kind of makes it worse. Because the hitman himself is exactly that sort of reactionary edgy of someone who's chief complaint with action movies is that they aren't "realistic". The character was outdated before he even hit the screen, and I suppose that's why mostly boomers thought it was a legendary flick and you don't hear all that much about it anymore.
He reminds me of Sylar, from Heroes. Same silly, emotionless edge from a weird-looking white actor. It's no coincidence both are from the same era, and Heroes gets even less mentions these days than No Country for Old Men.