Arkham Asylum is a true Batman experience not seen in a long time.
One of the first things you'll notice are the familiar characters that anyone would recognize even if they have only a little knowledge of Batman. Harley Quinn makes an appearance and is a heavy influence to the story as she helps aid the Joker through his devious plan. As dramatic and cinematic as the story starts out, the gameplay itself starts out somewhat slow. The first bits of action involve taking down a few goons, which throughout the game are mostly prisoners and Joker's henchmen. The combat system is relatively simple, but satisfying to watch. Most of it is mashing the attack button while switching between targets to avoid getting hit. But throw in some counters, stuns, batclaws, and other various gadgets including the batarang, and the combat can be really fun to perform at times.
Besides just being able to beat the living crap out of everyone, Batman is extremely stealthy. So it's no surprise that there are more than a few missions where Batman must bring down all enemies in a given area via stealth. During these stealth sections, all enemies are typically armed, evening the odds. There are various ways to take down an enemy while staying hidden, which makes these stealth task a lot more fun than they can be. They often require patience and careful planning. That said, it can sometimes be disappointing to run into another room filled with armed henchmen when you really just want to kick some more ass. But again, thanks to the many different ways to take down someone all stealth-like, it opens up opportunities for strategy and satisfying take downs.
There are a few number of boss fights throughout the story. Unfortunately you may not get to fight everyone you would actually want to fight. There are about four or five main boss fights, and sadly they, for the most part, require the same strategies. A few in particular have you fighting a few waves of your standard enemies, which is a little uncreative for a boss fight. And then the other common strategy that has to be performed is quick throwing a batarang, dodging, and repeating the process. Yet despite all this it's still a worthy and significant experience as far as the entire game goes.
A big feature that should be mentioned would be detective mode. This is activated by tapping L2, and it gives you a different perspective on the environment around you. It detects enemies through walls, can be used to decipher riddles, and even used to find areas that can be accessed with some of your cool gadgets. Detective mode, however, can make the game really easy for you. It's very helpful, and it's hard to complain about that, but it seems like something that should have limited use. However it is kind of an eye sore to look at for a long period of time, and that can be enough to switch back to normal at times, instead of playing through virtually the entire game in detective mode.
Batman: Arkham Asylum is also rewarding thanks to the experience earned during combat, and for completing specific missions. There are also a lot of riddles to solve, which also net a good amount of experience. Once enough experience is earned, upgrades can be unlocked such as stronger armor (more health), new moves, and other improvements to your gadgets. Solving all 240 riddles at any point in the game, including after the story has been completed, isn't as bad as it sounds. These "Riddler Challenges" ,to be more exact, involve finding riddler trophies, scanning certain objects that have some sort of significance to a clue, scanning hidden messages, finding interview tapes that reveal a lot about certain characters (even if they aren't seen in the game), and destroying chattering teeth found throughout Arkham City. Because of the large amount of riddles, many of them are easy to find, and in some cases in very lazy locations. But still it is something to do, even better after completing the story, and it is in a way fun and rewarding to find them all.
Least to say Batman: Arkham Asylum is a great action game, with mixed stealth and open world gameplay elements. Solving all of the riddles and completing the story should last well over 10 hours. Upon completing some of the Riddler challenges, other challenges will be unlocked. There are combat and predator challenges. Combat challenges are of course... combat challenges in which you have to try and get so many points while beating up some bad guys. Predator challenges take you back to some of the stealth sections, and you must perform specific maneuvers to earn a higher rank. These challenges are something to do after all else has been done, and they are really difficult to achieve the highest rank in, and are sure to give anyone looking for a challenge something to accomplish. As a bonus in the PS3 version of the game, Joker can also be used to play through challenges. It's pretty good for a free little add-on as well.
To add to the great action and overall well put together gameplay, Arkham City looks great, the sounds are wonderful, the voice acting is excellent (especially for the Joker's character), and everything else is well above par. Arkham Asylum is easily recommendable to anyone looking for a great batman game, or even just an action game for that matter.