NightSky has beautiful visuals, touching music, and it's one of those things that prove that games don't need to be extremely hard—or hard at all—in order to be fun. It does also include an alternative mode with much harder puzzles for those looking for a challenge. The only downside to the game is the price, but $10 isn't much at all. I very highly recommend this game.
Systems: PC, Wii, 3DS
It amazes me how people can still think up new Tetris-style concepts that are still fun. PiCTOBiTS is an addicting arcade game for DSiWare with fun chiptune music and a lot of different levels. In each level you try to clear different colors of blocks in order to create various different characters from oldschool NES games. If you have a lot of time to kill, check it out.
Systems: DSi, 3DS
Galcon Fusion is a real-time strategy game in space, with a ton of game modes, difficulty levels and achievements. It's addicting, in a good way, and can spawn numerous hours of game time to take up... time. Oh, it's also colorful and pretty. Highly recommended if you like strategy games or multiplayer games in general.
3D Classics: Kid Icarus
This is the original NES Kid Icarus game remade in 3D, with some other revamped features as well. One worth mentioning is that the game now has cool level backgrounds, so it's not always black. Basically, it makes for a super fun platformer and a worthy remake of the old game. My biggest problem with it is the fact that half the game is far too hard and the other half is far too easy. It seems to alternate between extreme difficulties. Regardless, this game is certainly recommended.