PixelJunk Monsters kills it. I bought it on the PS3 a few months ago and while I loved the first few levels, there’s a steep cliff where the difficulty curve should be, and I failed to climb it. For some reason during a hard month I revisited this game and I fucking LOVE it. It got me through some tough times. You have to embrace the cold hard truth that you will be playing the same levels over and over, you have to LOVE this. This is something old school, it is out of place with the low amounts of challenge we face in modern, casual-friendly games. However, the environment of the game is so pleasant:
You are moving back and forth, dancing, collecting gold and gems, building a system, and the replaying of levels is what is required to make the system PERFECT. Incidentally, this is surely by design; the game requires you to unlock harder areas by collecting rainbows, which you only get with a perfect score on a level, aka you didn’t let one monster through (you have 20 in your village, each monster you let through kills one, and normally you can win with only one villager remaining, BUT AT WHAT COST I ASK YOU? Save them all).
The environment is pleasant, the gameplay is well calibrated, with a few elements that perfectly compliment each other, and the levels and tower progression give you a great variety of play and strategy.
Incidentally, I balked for a while at buying the PSP version, which costs $20 compared to the $10 of the PS3 original. It is absolutely worth the money, however. The PSP version includes two add-on islands which represent a great deal of play time. The game is well-suited to the portable device and that’s where I’ve played the most of it.
Just assuming I won’t get around to writing up PixelJunk Shooter, the most recent release in the series, let me just add that it is awesome as well.