The first one or the new one?
Haven't seen the new one.
The first one though? Fucking awesome.
The important thing to me is that, even if someone has no idea about the Joker as a character could watch the movie and see an incredibly well made movie. It's a great story, the acting is world class, the way it was shot brings depth and emotion to every scene, and the details of the writing are unusually good.
As an example of the last, the background characters, and people with only one line, they have similar ways of speaking, a distinct almost accent in the way the lines are arranged. It ends up feeling like everyone in the movie is from the same place. You know how you go to a city, and there's turns of phrase, word choices that show up, even when different parts of the city have their own accent? That's what I'm talking about. Even De Niro's distinct way of speaking shifts to feeling like his character is from the same city as the clowns.
But, as a joker movie, it's just as successful. It tells his origin story from a fresh perspective. It does so in a way that even as someone that's complained about comic based movies doing origin stories instead of just telling a good story with the character/s, I was riveted. I am absolutely fine with the movie being another origin story because it's just that damn good.
If that's the one you're asking about, watch it. Even if you end up not enjoying it as much as I did, you'll at least have seen a movie that's crafted the way a movie should be.