Structure, Storyline, and Gameplay
. Gotham feels much more distinctive than a simple collection of high buildings and generic city architectures
The Joker, Two-Face, and the Penguin have all staked out zones of control and have sizeable gangs, while villains like Mr. Freeze and Killer Croc have remained focused on their own goals or gone more-or-less to earth. The Riddler makes no direct appearance, but puzzles, traps, and trophies positively litter Arkham City. The puzzles themselves are far more sophisticated this time around and often require the use of multiple gadgets or abilities.
Arkham City's story is driven by Batman's search for a cure to a Joker-caused disease and his primary investigation of Hugo Strange and the mysterious "Protocol 10." The plot is decent and the game moves along at a good clip, but the Hugo Strange plot relies on characters and relationships that newcomers to the Batman mythos may not be aware of.
The Joker remains the strongest cast member of Team Evil, even if he shares star billing this time around. One of the charges leveled against Batman in Arkham City is that his presence has created a crucible where the strongest criminals come to test themselves while his refusal to kill has allowed the evil he battles to fester and ultimately return to kill again. The Joker puts a personal face on this charge in Arkham City; the game makes it clear that the Clown Prince has a point when he sees himself and Batman as inextricably connected--even if Batman doesn't want to admit it.
Boss fights are varied and require strategy. Clayface made a cameo in Arkham Asylum; he's back for blood in Arkham City
In addition to the main quest there are a number of entirely optional side quests involving lesser-known villains. As a result, Arkham City is shorter than AA if one plays strictly through the main quests and ignores the optionals. Toss in the side quests and the game is at least as long, particularly if you're a completionist who needs to hunt down every trophy and solve all the riddles.
PC gamers also take control of Catwoman for a few missions, and while they're not vital to the overall storyline, she's quite a bit of fun to play. While she lacks Batman's array of gadgets, she's much faster in melee. Catwoman is also a playable option in the game's challenge maps, as is Robin.
Arkham City uses almost exactly the same controls as Arkham Asylum, but with a few notable improvements. Combat has been streamlined and now allows for double/triple counters, catching objects thrown at you, and the ability to use all gadgets in combat. Double-tapping the key for a particular gadget will quickfire it. There's a much wider assortment of toys this time around, including electrical guns, smoke pellets, freeze bombs, and weapon disrupters.
Mighty foot engaged.
The wide variety of gadgets underscores the need for strategy and the fact that Batman, while in peak physical condition, is still human. Attempting to take on a group of thugs with shotguns, even in a fully-upgraded Batsuit, is a quick ticket to a reload. The same group of enemies that'll trash you every time in a face-to-face confrontation can be taken out without a scratch by a combination of stealth takedowns, aerial attacks, batarangs, and your boot.