Atolm, I’m inclined to agree, Dark Souls was one of the best games I’ve played in forever.
Solo_Wing, I almost forgot about Journey, that looked super interesting. I’ll have to keep that one in mind.
Now to hunt around, and see if I could find one for <$50. Woop.
Journey really is a must-play. You may want to get the digital version so that you can play the remastered version on PS4 one day without repurchasing it (in theory).
I’ve now basically finished with the Playstation 3’s library and will sell my console soon.
Some further thoughts:
I tried God of War 1 and God of War Ascension. These appear to be solid action games. I finished similar games such as Shinobi (PS2) and Bayonetta previously; God of War is comparable to those. I didn’t finish any of the God of War games though; I need something more to keep me motivated to reach the end of a game these days.
As mentioned in The Last of Us topic, I played through all three Uncharted games, and The Last of Us. Naughty Dog has come a long way since the days of Crash Bandicoot, with the story driven nature of their newer games keeping the shooter/platformer formula interesting. I’m not saying that the quality of the Uncharted stories are great - they’re basically popcorn action movie stories - but overall experiences are solid. The Last of Us is the really polished experience from Naughty Dog and like @UrbanReflex I recommend it for reasons mentioned in The Last of Us topic.
I made a separate topic to discuss Flow, Flower, and Journey.
Another game I played through was The Unfinished Swan, a magical and unique game. I also made a separate topic about it, but it looks like no one else played it?
Some other games that I tried:
Lair. Horrible controls. I wish someone would make a new dragon riding game with good controls.
Ratchet and Clank: A Crack in Time. I played through a few levels of this; a fairly standard 3D platformer, not bad.
The Golden Compass. This game was only $2 (and published by Sega!), so I thought, “why not?”. I now understand why the game was selling for $2.
LittleBigPlanet. Like Ratchet and Clank, a fairly standard platformer (2.5D though), but with lots of customisability. I can see this appealing to the Minecraft crowd. If I was younger, I would probably invest more time into a game like this.
I also picked up Okami HD on Playstation Network as I had been wanting to try it for years (since it was released back in 2006 on the PS2) because of it’s unique art style. I likely won’t play through the whole game before I sell the PS3 as the main story is 37 hours long according to howlongtobeat.com. That’s too long for a single video game in most cases. But I’m glad I was finally able to try this unique looking game.
I decided not to get Demon’s Souls. As with Okami, Demon’s Souls takes over 30 hours just to finish the main story. A game has to be exceptional to justify that kind of time investment for me these days (almost a full working week). However, I do appreciate the recommendation. I might check out Dark Souls at some point though since you speak of it so highly, @Atolm . 
It’s a shame that I was not able to finish Heavy Rain due to that save file glitch, but now that a remastered version is coming to PS4 (as well as Beyond: Two Souls), there may be an opportunity in the future to try it again. It’s good that most of PS3 classics are available on or coming to PS4 - basically all of the PS3 exclusives that matter have been ported to either PS4 or PC. Hopefully Ico and Shadow of the Colossus will make their way to PS4 before The Last Guardian is released too.