Let's see, I'd reccomend Bayonetta, Darksiders and Batman: Arkham Asylum. All are easily found under $20 and are quite good. Bayonetta has some of the best Devil May Cry-style gameplay out there, Darksiders is basically a fun Zelda clone, and Batman is a beat-em-up with some Metroidvania elements (collectibles) thrown in. They're all great, and if you get Arkham Asylum's GOTY edition none have DLC or anything.
The most fun game I've played recently has been Ni No Kuni. It was made by the company that made Dragon Quest 8, and this game (while admittedly not as good overall) was one that might just end up on my top 10 list. I think you can get the game for $50 on Amazon, and I further think that you can still even get the preorder monster. That is, I heard people were still getting it.
Playstation All-Stars is... fun. Especially with others.Do yourself a favor and download the DLC characters now! They're only free for a limited time, and you can download them without owning the game. I bought it at $40, and while I think the game has a lot of good things, the roster just feels so incredibly lackluster. Prepare to be annoyed as you patiently explain to your friends who all these people even are. But like I said, it's fun. I just think Sony could have put a little more effort into the project, seeing how much potential it had and all.
There's also a sale going on this Tuesday. You can vote for which games go on sale from the Playstation Store. If Journey goes on sale it might be your kind of thing. Short, but neat. There's a lot more interesting games potentially going up for sale, so check it out and vote for which you want to go on sale.