I like RuneFactory, Puzzle Quest: Challenge of the Warlords, Luminous Arc, and a few others, but those are my favorites.
RuneFactory is deeper than most Harvest Moon games, Puzzle Quest is just fun (like Bejeweled, but with hit points), and Luminous Arc has an interesting story and lots of fun characters (even if I can't stand Heath's voice).
And I plan to get Fire Emblem DS whenever it comes out
Even though I hate Marth.