If you're after wackier, unknown titles, I'd recommend perusing the PlayStation Store. There's lots of zany stuff to uncover there (try Noby Noby Boy, flower and Everyday Shooter). At retail I'd recommend the Uncharted series, Heavy Rain, God Of War (the Collections and III), Red Dead Redemption (assuming you don't already own it on another platform), and -- if you want narrative heavy wackiness -- the Yakuza games, which are amongst some of my favourites on the platform.

Hope that helps!

Uncharted dual pack and Uncharted 3.
Batman: Arkham City/Asylum

Since you're loving Infamous I'd definitely recommend picking up Infamous 2.It improves upon the original in just about every way imho.

Also, you get a head start in the morality meter for which ever side you beat the first game on. For instance, if you beat the first game with full positive karma, collected all the blast shards and dead drops, then you'll start Infamous 2 with the title of Guardian and gain some XP to use right from the get-go. It's awesome

Good luck with Demon's Souls. I hope you ordered an extra controller too, because you'll no doubt take sladgehammer to the current one after attempting to get to the first boss, finding the right path, grinding for hours, just to get slaughtered within a few seconds of the boss fight starting.
... Anyways, good luck o.o

Bumping so people remember this exists. We've been getting a few too many threads asking for recommendations in the PS3 section.

I highly recommend

-Metal Gear Solid 4
-Heavy Rain
-Flower
-InFamous
-Call of Duty Black Ops

As these are my top five favorite games on the system.