I think a lot of people went in to this game having decided they already hated it before actually playing. That said, there are also a lot of people on the other side of that, which is where I fall.
The characters and setting are really great here. It was absolutely awesome to see members of the Justice League (and other DC characters), as well as Metropolis, in a AAA setting like this. Additionally, the story is rock solid. It's not the greatest story ever told in gaming or anything, but it's genuinely really enjoyable and well-paced. Also thought the combat and traversal both played very well.
My two main gripes. One - I wish the side content was a little more fleshed out. There's not much variety at all in the gameplay of the missions, and there's not anything rewarding narratively, just upgrades for your character. And having to kill enemies using a certain mechanic can sometimes be annoying depending on which one it is. Two - that Superman fight was way too underwhelming considering, well, it's Superman. The Batman and Lantern encounters were the highlights for me.
Overall, I felt like I was one of the only people who was genuinely excited for this game for all of this time, and I'm glad it ended up being good!