idk which PS3 games are essential or nice to have at least? Consensus I'm getting around here is that Tales of Graces and Xilia weren't really as well received, Witch and the Hundred Knights didn't review all that well, uh, what's the deal with airline food? how are Uncharted and Infamous?
Some games I recommend:
-3D Game Dot Heroes (before From Software conquered the world with Dark Souls, they made this awesome homage to and parody of 2D Zelda games with really, really silly weapons and the option to build your own hero out of voxels)
-Ni no Kuni (it's a lovely classic JRPG adventure)
-Folklore (gameplay isn't that special, but the atmosphere is great and the story is something you don't see in every JRPG. Reminded me of Shadow Hearts at times)
-Heavy Rain / Beyond: Two Souls (interesting experiments in interactive storytelling at the very least)
-The Guided Fate Paradox (sure, it has angels in maid outfits, but this roguelike is a ton of fun!)
-Atelier-series (I love these games. Doesn't hurt to try atleast one of them. Preferably Totori or Ayesha)
-The Last of Us (great story and characters, but it's totally okay if you don't like the cliche setting)
-LittleBigPlanet (cute and fun platforming action. It's Sony's excellent rebuttal to Nintendo's platform games)
There are also so small but amazing gems to be found on PSN. Journey is a no-brainer, but I'd also recommend Rain and Tokyo Jungle. Or hey, play a modern Wizardry game because, why not?
Xillia and Graces both have their flaws, but they're enjoyable games. You won't love them, but you will like them.
Uncharted and Infamous: wouldn't hurt to play atleast one game from both series. Older installments very cheap and very easy to find anyway. Uncharteds are very polished action adventures and they're so much fun, you'd probably won't notice the flaws (like re-used enemies or repetitive fights) until after finishing it. It's Tomb Raider without boobs and that's not a bad thing. The Infamous games have some great ideas but drop the ball when it comes to the moral choice system and stuff. Still a blast though.
Valkyria Chronicles seems to be the big one, but... again, PSP sequel which I've largely heard was just as good, and I sort of want a PSP anyway, especially since XSeed's taking their sweet time TitSing Steam.
I love my PSP. Lots of its games are available on PSN for Vita, though, so if you're not dead set on owning physical copies it might be best to buy a Vita instead. It's more expensive, but a lovely, versatile piece of hardware.