List now updated with why i like the games, just for you
Valkyria Chronicles:
This is the best singleplayer game i have played this generation and the best RPG i have played in years (even though it isn't a traditional RPG). The graphics are both unique and beautiful, the characters are lovable, the storyline is epic and the voice acting is top notch (if you use the original japanese voices with subtitles that is. With english voices it is only above average). The gameplay while it may seem basic at first does deepen as enemies become smarter and stronger and the abilities of your units increase. The music is also utterly brilliant.
Resistance 2:
Great little shooter, above average single player with fantastic graphics and some brilliant cinematic moments (basically every boss in the game is just awe inspiring). The coop is where this game shines though, up to 8 people can team up to fight hordes of AI enemies as different classes, each as important as the next. I didn't care much for the competitive multiplayer though.
Killzone 2:
I'm sure you know enough about this one already

. Great single player, if a little short, with really fantastic AI. Boasts what is imo the best competitive multiplayer FPS the PS3 has to offer.
Metal Gear Solid 4:
Great story, great graphics, great characters, great music. The controls, while clunky are better than the previous games, the storyline is good but a little mental in places, really helps if you play it through twice and refresh yourself of the story of previous games so you better understand character motivations. The multiplayer had loads of potential but was fractured early on by DLC and fell into obscurity. Very marmite game, you love it or you hate it.
Ratchet + Clank Tools of Destruction:
Great old school 3d adventure game. Really reminds me of some of the greats such as Banjo Kazooie whenever i play it. Contains some of the whackiest weapons you'll ever see (groovitron grenade! Killer robot dance party is go!). It has it's flaws but it has so much charm i overlook them.
Ferrari Challenge:
Best next gen racer on the PS3. It's similar to GT5

as it has sort of semi realistic handling. Great graphics and great cars, if you like your racers this is worth a punt.
Ninja Gaiden Sigma:
Graphics are crap for next gen standards but it's still the best looking incarnation of the original Ninja Gaiden. Some argue the gameplay mechanics are also the best but i won't comment on it myself. Good buy if you haven't played the original game.
Buzz:
It's buzz, enough said
PSN Games:
Super Stardust HD:
Imo the best dual stick shooter i have ever played. Beautiful graphics, frantic gameplay, great weapons system and loads of modes to keep you entertained.
Wipeout HD
It's wipeout, but HD! Great graphics, 1080p @ 60FPS 90% of the time (it lowers the resolution on the fly in busy moments, you don't notice it tbh). The multiplayer has recently been revitalized due to a multiplayer patch. Great buy for the money, its around £12.
Echochrome
Interesting puzzler, try the demo, i can't really explain it
Tekken 5DR
Just got into this, solid fighter tbh, graphics are a little dated though. Can be picked up cheap on the psn (around £15). Be warned, the netcode is rubbish.
Pixeljunk Monsters
Classic tower game action!
Flower
Can't explain, just buy it
