Welcome Rancid!
I actually can't add much more than RenegadeRocks just posted- those games he mentioned are the ones to get IMO.
Uncharted 2 is brilliant - and
Uncharted 3 follows up on that. Both are immensly better than the first part, and IMO, more enjoyable than Last of Us (although I just started playing it - but it's quite a serious theme).
Then, as was mentioned,
God of War 3 is a awesome. If you do get it, perhaps play it on normal, although even then, it can be frustrating at times since it starts epic. But it's definately one of the show-case games on the PS3 you won't regret if you fight your way through it. Forget about Ascensions.
Then, personally, I'd also get
Wipeout HD if you like futuristic racers. It's something, if I'm not mistaken, that's nothing like you can get on Xbox, so it might be something unique. I'm also pretty sure you could get it rather cheap. What makes this a great game is the sense of speed, great sound and there's a lot of skill involved. It might be difficult in the beginning, but it's soooo satisfying when you get the hang of it and start mastering the quicker speed modes.
If you want something to entertain guests with a lot of fun factor -
LittleBigPlanet 2 is hard to overlook. The perfect game to have when you have people over, especially girls.
KillZone 2 as mentioned is brilliant - though it's probably hard to impress a gamer coming from the Xbox. I personally think the single-player experience is better in
KZ3 - the mechanics are a bit better and make it a bit more enjoyable ride. The wow effect IMO is also a bit bigger. I do prefer the artistic visuals and the online multiplayer in KZ2 better, but I still think if you're new to the whole KZ series, part 3 is the more enjoyable ride.
Among my favorite games is also
MGS4. Very special game and a definate must-play IMO, especially if you are thinking of trying out MGS5 on either Xbox One or PS4 eventually. I actually prefer
MGS3 too, but that's only a HD release of the PS2 game. Both are very recommendable though and I'm sure it's a type of game, you won't have experienced on Xbox (I think it's very unique in the way the story and gameplay get you hooked on the game - Hideo Kojima is simply a genius).
Now, as for enjoyable cheap mini games that are DD-only:
Definately check out
Super Star Dust HD. Very good platform shooter with great sound in FullHD. Highly addictive. If you're unsure, check out some videos on YouTube. For the price it costs, it's great.
You may also like some of the
PixelJunk games. I really like Racers (fun when you have lots of people over), but Shooter is good too or Eden - both can be played co-op, but I don't think online. They are just some nice stylistic mini games that pose a great challenge inbetween.
Hope you get some enjoyment out of the large investment you just made! :smile: