This is meant as a companion thread another thread of mine to be found here
please explain to the best of your ability why you think it is the among the best box art, how it grabbed you, layout, etc. professional critiques welcome.

Always bet on Duke!

Classic.
EDIT:
Fix'd.

link is broken ...I just get Moby games in a large white box.

I've always loved the box art for all three MechWarrior 2 games since they match.

To me, the demons look more like chavs running away with a car stereo than demons who're about to tear a guy limb from limb. I preferred the minimalist Quake series box art myself.

Diablo 1 is pretty awesome. Deus Ex is EPIC. Resident Evil 4 (GC) is just pure awesomeness.

System Shock 2.

Don't think this is THE best box art, but it's just amazingly done and epic.

My vote would have to be the art for Deus Ex. After all, it got me to buy a game I'd never heard about before.

Sanitarium
http://www.mobygames.com/game/windows/sanitarium/cover-art/gameCoverId,16878/
Perfectly conveys what the game is about. A psychological thriller.
Also, Stranglehold. Chow Yun-Fat shooting people in the face! I bought it immediately.
http://www.mobygames.com/game/xbox360/john-woo-presents-stranglehold/cover-art/gameCoverId,143588/
Amazing game. Like Max Payne on steroids.
KOTOR did have great box art though. You're right.

The Beast Within
establishes that the game is horror, for-shadows events in the game, simple, clean and terrifying and elegant at the same time
Evidence: The Last Ritual
Hands down, best game packaging ever, extremely clever
Shadow of Colossus
I like this box simply because it literally does what the title of the game says it puts the main character and his horse in the shadow of the colossus

Phantasmagoria's was pretty good. Too bad the game sucked ;)
http://www.mobygames.com/game/roberta-williams-phantasmagoria/cover-art/gameCoverId,149102/

I always loved the looks of evidence. THATS how you make a sweet box :P

Oh, how can I forgot this? The first two Monkey Island games, excellent art by Steve Purcell.