The stealth is from...
Tom Clancy's Splinter Cell
The Metal Gear series may well have been the first game to use stealth as a major gameplay mechanic, but the style of Batman's sneaking is much more akin to Sam Fisher's shadow-dwelling. Like Sam, Batman's got gadgets to scan the scene and plan his attack in advance. And both have a tendency to drop down from above, take out their target and then vanish again into the darkness.
Above: Splinter cell let you use thermal imagery while hanging in shadows
The forensic aspects are from...
Condemned: Criminal Origins
Scanning a level for forensic clues was one of the tastiest new treats when this generation kicked off. Seeing UV traces under your forensic lamp in Condemned added a tangible sense of mystery and horror that works just as well in Batman's dark comic universe. Following breadcrumb trails of tobacco makes us feel like kick-ass detectives, which is why this rocks.
Above: Exact. Same. Thing. Not that we're complaining - it's way cool
The console crash trick is from...
Metal Gear Solid
There's a very nasty moment in Arkham Asylum where the game delivers a scarily accurate rendition of a 'red ring of death' crash, before apparently rebooting the game back at the beginning (only for the Joker to take Batman's place). This is very similar to Metal Gear Solid's Psycho Mantis fight when you switch controllers, to be greeted with a black screen with 'HIDEO' in place of SD TV sets' AV channel 'VIDEO' tag.
Above: What an incredibly nasty trick. We really thought it had gone again
Above: And MGS's extremely clever fourth wall smash up
Scarecrow's nightmarish mind tricks are also highly reminiscent of Eternal Darkness' sanity effects. The morgue set-piece, if not a note-for-note replica, is at the very least a tight harmony line with Silicon Knights' masterpiece.
The upgrade system is from...
Ratchet & Clank
If you're talking about games that let you revisit previous sections with new skills to reach new areas, you could argue games like Super Metroid or even Mickey Mouse's Land of Illusion did that aeons ago. But in the 3D era, Ratchet & Clank did it best first, drip-feeding you new gadgets and weapons at just the right pace to keep up with your own skill development and letting you get to the most secret places right at the end of the game.
Above: Mickey Mouse: Land of Illusion, Super Metroid and Ratchet & Clank
So why is Batman: Arkham Asylum such a big deal?
You mean big enough to win our coveted Game of the Year award? Because it provides a dark, authentic comic book world and fills it with supremely playable gameplay to boot. With just the right mix of puzzles, combat and exploration, it's simply a class act from beginning to (just before the) end.