I know that I may be in a minority, but I for one loved Jared's Joker in Suicide Squad. The look, the acting, the dialogue, the mannerisms, the whole shebang. As I do all versions in movies and shows so far. They all bring something new and interesting to the character. The Joker is a character who's insanity and appearance morphs from one version to another. Always has and always will. But all of the versions kept the core of the character. Batman's arch-nemesis who is the biggest scourge upon Gotham and find humor and joy in crime. Also the characters visuals vary but almost all are consistent in the white face, green hair, red lips and purple suit departments.
Leto's Joker is taken as a modern day gangster which is not only new but it may be the first time the character has been 'modernized' in the full meaning of the word. In his original appearances, Joker very much resembled a 40's gangster with a clown twist, and for decades has continued to do so. Ayer and Leto brought us a 2010's gangster with the same clown twist that defines him.
He is also the first live action Joker to have a long history with Batman (not including the 66' version since any history doesn't play into the show or it's movie very much). The first Joker to have a Harley Quinn besides him. He is also said to influenced by Grant Morrison's take on the character, which is the best way to approach Joker that one could take, simply cause Morrison stated that the Joker reinvents himself from time to time, thus giving the actor, directors and the studio a way to play around with that idea for future movies. As I said I personally loved this version. I wanted a Joker who for once doesn't have any sort of perma-smile. Loved the permanent grimaces we've gotten through the years, but this gives us a Joker who can be serious and up the creepiness when the laugh comes out.
Also, I loved the laugh. Again, loved everything. The teeth fillings and scars were great editions especially for a version that's battled Batman for two decades. The tattoos are great cause they make this version unique to all the ones that came before. If someone asked me what would I like to see Joker look like on the big screen before Suicide Squad, I'd probably say: a mixture of The Dark Knight Returns, Batman R.I.P. and All-Star Batman and Robin.
What we basically got was that and so much more so I'm an extremely happy camper as you'd imagine. Of course I know a lot of people didn't like this version and want a more, let's say, 'classic' Joker which I respect. And while for now I hope they stay with the same vision they started, they do have the 'Morrison' loop-hole to change up the character if the so wish, and I'd be interested to see what they would come up with next.
Leto's casting was perfect from start so I really hope he stays on for multiple movies, which last I checked he said he'd love to, despite his anger at the editing of his role in Squad. The editing really is this character's only enemy in the movie for me since Leto obviously put a ton of work in his performance. His role was small, as we should have known it would be since it was a Suicide Squad movie, not a Batman, Harley Quinn or Joker one.
Hope to see him as the primary antagonist in future solo Batman movies so he can shine in all his crazy glory. I think he would win some people who disliked his performance over then. If not, they could at least dislike it when he has the proper screen time he deserves.
Sorry for the long post, just had to add my opinion on my favorite villain and second favorite character ever. Cheers