Portable Ops was interesting but the controls were garbage and it wasn't a Kojima game.

Peace Walker is the most impressive handheld game I've played, a satisyingly playable, free camera third person stealth action game. The story is pretty good and co-op Metal Gear is just as fun as you would hope it could be. It's probably best to play the HD remaster on PS3/360. The game is a little easy, though.