Arkham City is a fantastic game. Honestly, the best game I've played this year so far. Of course I'm currently missing a few of the contenders; the much-raved-about Skyrim and Uncharted 3.
But Rocksteady have definitely impressed me with their ability to take an excellent game and produce an even better, bigger game without sacrificing anything at all. Combat has improved, the environment has improved, the scope and uses of gadgets has improved, even the Riddler challenges have improved. Boss fights improved, though that was already a weak spot in the original so I was expecting improvement here. Generally, I just felt even more that I was Batman than the last game, which makes it a roaring success in my book!
I look forward to the next one! Will there be more Joker? Joker Jr.? All that matters is that I take down my true nemesis once more... all of those blasted Riddler trophies! D:<