I'd recommend the following, based on your liking for MGS4 and FFXIII:
Uncharted: Drake's Fortune (this is a shooter to a degree, but if you like MGS...)
Valkyria Chronicles
Demon's Souls (pre-order this baby - my current GotY)
I'd also highly recommend checking out LittleBigPlanet. It has the best multiplayer component of any game released this gen, in my opinion, and the drop-in/drop-out nature of multiplayer makes playing with friends a breeze, either online, offline, or both.
If you're a fan of platformers or anything Nintendo-ish, this game is for you. It's cute, hilarious, mischievous, and downright fun all around.