Okay so I'm normally a Grand Masters player but after a few folks recommending Tetris DS I can see why it's their favorite. The speed ramping is perfectly paced, the NES music and scenery is warm and welcoming, and the variety of modes on display is exceptional.

Combine this with the base marathon mode win condition of 200 lines cleared and you have an incredibly compact Tetris iteration that encourages you to return and replay at your own pace without making you slam your head against the wall.