People already just about told off what games I was going to. Outside of maybe One Piece: Unlimited Adventure and Shiren the Wanderer (the later having just come out).
So here are some games that are coming out soon that you should put on your check list: Monster Hunter 3, Fragile, Arc Rise Fantasia, a new Zelda Twilight later this year, and a few others I either can't remember off the bat or I don't know the release dates to. Tales of Graces (or some random Tales of game) is coming out eventually, as is Dragon Quest 10. DQ9 is slated for the DS later this year. I believe they're all rpgs and adventure games with some form of story... 'Cept for maybe MH3, which is pure awesome.
You should also invest in a game cube controller and memory card, then stock up on GC games you may have missed out on. Such as the first Tales of Symphonia that just about everyone recommends, Skies of Arcadia, and Paper Mario: TYD.
Edit: Oh, and Rune Factory Frontier if no one has mentioned it yet. It makes Harvest Moon and other farming sims absolutely epic with its dungeons and general fun. Yes, you too can beat a giant squirrel to death with a watering can.