It really depends. Are you a big batman fan? Or do you like your games to chew you up and spit you out?
Batman AA is a great AAA title but is beaten in 10 hours or so and personally, the challenge maps aren't that great. Although if you think you might enjoy them it adds a lot of playability and has the promise of free dlc.
Demon's souls meanwhile should take much longer to beat but takes A LOT of backtracking. But the enjoyment of succeding is unlike anything else.

Never Heard of demon soul either...

Batman AA is a mega hit

Demon's Souls!

You can't really go wrong either way, though.

Words Of Wisdom said: Batman AA. Don't bother with a mediocre game like Demon Souls.

I swear you're doing this just to spite me.  >_>

Batman: Arkham Asylum is hands-down one of the best games of this generation.

Batman AA

Demon's Souls looks depressing to me

@the kitchensink

I played it, its great but not as good as MGS4 & SMG!

Batman AA is the real deal. Should have an extra A at the end. Buy it

Didn't say 'the' best

But it's a fantastic game that deserves to be in the collection of anyone who owns a 360 or PS3.

yes it is very good in that way kitchensink!

I love the stealth elements & once again it proves how brains are more important than muscle

Batman I've heard is a 7 hour journey, if you aren't bothered about all the riddler clues then rent it. Definitely pick up Uncharted 2. Demon Souls has received some good reviews, I wouldn't write it off just yet. I'll say rent Batman, buy Uncharted 2 & possibly Demon Souls as (DS) is about 100 hours gameplay, more for your money. Just my thoughts..