I have a little soft spot for Batman: Hush as it was one of my first Batman comics. I liked Jim Lee's art and the reveal of the Riddler.
He's clearly a hit in the sense that he's become a recurring member of Batman's rouges gallery, which happens maybe once every 5 or 10 years at this point. As a character in and of himself it's harder to say. He's got an inspired visual, and being a dark reflection of Bruce Wayne rather than Batman means he occupies a niche that's not as crowded as some others. The main problem is that the actual plot of the story that defines him is such a damn mess, and to top everything off seemingly ends by denouncing him as a sad pretender that really could have been anyone, just a pawn in Riddler's plan. Heart of Hush does a lot to mitigate that (with a few tweaks it could easily work as his first appearance), but somehow I feel like he's still struggling to overcome the sloppy plotting from the original Hush. It also doesn't help that h's motivations severely limit the type of story you can tell with him, which is a problem he shares with other villains who's only goal is "Destroy Batman and/or Bruce Wayne".
As of now:
All-Star Batman, Batman, Doom Patrol, The Flash, The Fix, The Flintstones, Green Valley, Hadrian's Wall, The Hellblazer, Moonshine, New Super-Man, Suicide Squad, Superman, 'Tec, Unfollow