I remember really enjoying this at launch, though it maybe wasn't my favourite of the series. I replayed through all of them lately though and it's easily my favourite, and massively under appreciated. I honestly think if they released a remaster of it on current gen, with 4K/60FPS and ray tracing etc, we would have dozens of LTTP/RTTP threads here really praising the game.
The game still looks amazing, and the art direction really carries it.
The fighting mechanics were elevated from the previous games, and really perfected.
The toolbox and mechanics really go a long way in making you feel like Batman.
The bat mobile weren't as overdone as I remembered, and I actually thought they were pretty fun.
For an open world game, it feels way different to other games in the genre.
Overall, I think comparing it to other games today, the closest something gets would be Spider-Man on PS4, but the side content in Arkham Knight and the world design really eclipses it. Arkham Knight just kinda breaks the mould.