Well you could try Fallout 3 if you haven't already or Red Dead Redemption.

Fallout 3

Just cause 2.

inFamous 
 
Oh and you can check out this open world page on the site. Not all are PS3 games, but you can pick out the ones that are.

Defininently Just Cause 2 or Red Dead Redemption.

Red Ded Redemption <- I hear this is good
Infamous 1 or 2
Borderlands

Fallout 3 and inFamous are both great open world games. Actually RDR is pretty good too.

oblivion, burnout paradise

Saints Row 2

Fallout 3, f'shiz.

Everything said here is pretty great, my favorites being red dead redemption and infamous.

my favourite by far is the S.T.A.L.K.E.R series.... waaaayyyyyy to many hours of my life have gone into those games....

" Well you could try Fallout 3 if you haven't already or Red Dead Redemption. "

I would say Red Dead Redemption, it's the only open world game that kept my attention long enough for me to finish it.

" Saints Row 2 "

My favorite open world games you can play on the PS3 are Red Faction and Infamous.

"

Just cause 2.

"

Red Dead Redemption and Just Cause 2 for sure. If you want more RPG, go snag Fallout 3.