Metroid Prime Pinball (MPP). I played some of the first Metroid Prime, and some of the original Metroid, but I couldn't get into them. I love the Metroid-style Castlevania games, so I can't see why I don't like the original Metroid. I think I'll try Super Metroid when it's released on the Virtual Console; I've heard it is much better. I might try Metroid Prime 3 if it gets good reviews.
Anyway, MPP is awesome. I'm not even the biggest pinball fan around and I thought so. It has 2 full boards, and 4 boss boards (consisting only of the bosses. That doesn't sound like a lot until you realize how ridiculously hard it is to unlock the last 2 boards. You end up playing for hours just to get them, and once you do get them you'll keep playing to beat your high score.
Graphics: It looks really good, and definitely has a pinball table feel.
Sound: It's been a while since I've played it, but I remember some nice tunes. It does its job at any rate.
Difficulty: Through the roof. Good luck unlocking the last 2 boards.
Controls: Shoulder buttons for flippers, ball launches itself. Could it get simpler? My only gripe is you have to shake the table by touching the bottom screen and moving it with your finger; it's hard to do when you're trying to shake the ball out from between the flippers.
Design: The DS is a perfect pinball system. The two screens allow for a full-sized table without it scrolling or looking flat. The only system that can do pinball better than this is the Virtual Boy, and I don't think they're still releasing games for that.