Play as Batman and occasionally as Catwoman. Robin and Nightwing are available in DLC challenge maps. Explore, fight, and solve crime in 3rd person throughout Gotham. Has a solid story and even more solid combat system, aside from the occasional glitch.
I would say that for its time, Batman: Arkham City has top of the line graphics. The Batman character model is well done, coupled with the environment, this leads to some impressive views when sitting atop a roof or overhang. The game is well optimized too. With graphics on highest settings I never dropped below 60fps.
The voice acting is very well done, significantly enhancing the experience. Most sound effects and background noise are spot on as well. What really bothered me in this category however, was that the simple thugs you're fighting 80% time, had really redundant dialogue that grated on my nerves after 20+ hours of game play.
Most of the time this game ran very smoothly. I commend how well combat flows, not to mention the fun variety of side missions and overall story. However I did often find myself "cheated" in combat, with enemies sliding ridiculous distances to score a punch outside of my peripheral vision. The combat system is easy to learn, hard to master, allowing you to jump right in, but still enjoy the combat hours later as you learn to incorporate new abilities into your fighting style.
I really enjoyed this game. The story kept me involved, and the side missions were interesting enough to give a breath of fresh air. With the quality voice acting and graphics, it's almost like watching a movie. The combat is satisfying, and entertaining. The freedom of movement throughout the city is great too, grappling, gliding, sliding, sneaking, and running between and to your foes.
Although new game plus is implemented, allowing you to go through the game again with your upgrades and skills unlocked, there's not much more to be gained entertainment-wise. The story-line and game play albeit being very fun, have no real deviation from the first time through. There are a plethora of DLC additions and challenge maps adding many hours of additional game play, but I've found these to be extremely tedious after the first few hours. (If you're looking to 100% this game expect to spend close to 60 hours repeating dozens of challenge maps over and over with every character,)