Pretentious artsy games? The only ons I can think about of that caliber are Flower, Journey, and The Unfinished Swan, but those are already on your list, so I can't really help you there,
I can, however, give you a list of some PS3 exclusives I would recommend to anyone.
Uncharted 1, 2, 3 - Action shooters that play like movies
InFamous 1, 2 - Super hero action games with parkour
Killzone 2, 3 - Perty shooters with bang bang explosions.
Resistance 1, 3 - FPS with extremely interesting weaponry (2 was an attempt to merge the series in a CoD direction. Didn't work.)
Ratchet and Clank Future: Tools of Destruction, Quest for Booty, and A Crack in Time - Made by the guys that made Resistance. Funny third-person-shooter/platformer hybrid with awesome weapons.
Sly Cooper 4: Thieves in Time - Stealth platfomer with a great sense of humor and art-style.
LittleBigPlanet 1, 2 - You already know about these, but 2 improves on the base formula of first game and makes it even better.
Playstation All-Stars: Battle Royale - Want a good Smash Bros. clone? This is your game.
Metal Gear Solid Trilogy - Won't be out until later this year, but has every Metal Gear Solid game in one package. Stealth games with super-long, movie-like cutscenes. Bring popcorn.
Valkyria Chronicles - Strategy JRPG with B-E-A-UUUUTIFUL watercolor aesthetics. God damn the game is gorgeous.
Disgaea 3, 4 - Grid-based strategy JRPGs with great amounts of humor and epic attacks
Persona 3: FES - Highschool simulator where you have to make friends and kill monsters with a supernatural power known as Persona.
Ico/Shadow of the Colossus HD Collection - Some of the most beautiful PS2 games remade for PS3. Ico is a interesting sort-of escort quest while Shadow of the Colossus is entirely epic boss fights.
HD Collections for Sly Cooper, Ratchet & Clank, and Jak & Daxter. The PS2 platformer trio never looked so good. Your chance to play every one of those great games in HD.
Demon's Souls - The predecessor to Dark Souls. Mind-numbing difficulty mixed with RPG elements makes for a great experience.
God of War Series - Hack and Slash on a scale of epic proportions. Main Objective: Eliminate the entire Greek pantheon. Have fun.
Heavy Rain - Another game that plays out like a movie. Focuses on 4 people as they try and unmask the murderer who's been drowning children all over town. An engrossing story that really emphasizes player choice. Can really make you feel uncomfortable, too.
Modnation Racers - Excellent kart racer in the same vein as Mario Kart. Think LittleBigPlanet as a Kart racer.
Hope this helps!
