Seems all I play in terms of gaming now are either on portables or PC, so I have a LOT of suggestions.
Lock's Quest (Think Tower Defense + ability to fight, have summons, etc. Frantic but fun)
Castlevania (truth be told, I like PoR best, but both of them are nice with OoE to look forward to as well)
Advance Wars: DoR (AW
S was stupidly broken, but the grittier one is a nice title)
Front mission First (or 2089 if you understand Japanese. Both games are REALLY fun TBS)
Shiren: the Wanderer (If you like Rogue-like RPGs, then this is probably the BEST one out there commercially.)
Izuna 2 (Second-best Rogue-like, it's pretty innovative with a nice crafting system but a bit short)
Etrian Odyssey 2 (the first one wasn't bad, but the second one kind of trumps it in many ways. Classic sort of dungeon crawler, lasts you a while)
Osu! Tatakae Ouendan 2/Elite Beat Agents (2nd one uses innovations found in the first one, but both are good (at least, in theory and not songs))
Phoenix Wright (of course...)
Hotel Dusk: room 215 (again, of course...)
Civilization Revolution (It's no Civilization, but it's one of the best approximations out there))
N+ (for random seconds/minutes in your day)
Tactics A2 (if you're going to get it, get 2 and not one. It's not a bad game, but the story is..definitely lacking)
Puzzle Quest (kinda broken, but still quite fun)
Meteos (Duh...if you can find it, get it)
Planet Puzzle League (What's that? Tetris Attack with Multiplayer??? Awesome
)
Age of Empires (Again, it's no AoE, but it's a nice approximation)
Now for the Japanese stuff...
Dungeon Explorer: Warrior of the Ancient Arts (It's probably available in the US, just haven't seen it. It's very much like Diablo, multiplayer is sadly lacking though)
Time Hollow/Sigma Harmonics (SH is better, but both have sort of this "point-n-click" adventure mystery thing around them)
Rhythm Tengoku Gold (Fun to play, a VERY good import (you need to know like 3? words: Taachi (touch), hajiku (flick), and one more (the word for lifting your stylus))
Ys 1 & 2 DS (It's a guilty pleasure of mine, not everyone likes Falcom, but it's a good collection)
ASH (Archaic Sealed Heat. The game is a FUN TBS/RPG game, but the character designs look as bad as Fire Emblem DS)
Fire Emblem DS (Of course...)
Disgaea DS (Coming out, both in NA and JPN, big title)
There's a couple more, don't come to mind atm tho
Lastly, GBA games...
Riviera: the Promised Land (Dating-sim meets RPG, it's better than it sounds)
Yggdra Union (FUN game, a bit strange to get into tho)
Ninja Five-O (It's REALLY cheesy but also fun to mess around with)
Golden Sun 1 & 2 (Of course)
Hmm...there's more, just can't think of many off the top of my head.
If you could specify what genres in particular (I know you said RPGish, but perhaps some other games on systems that you like?), I'll be able to give you a pretty good rundown of Eng/Jpn titles available (Yes, I am a handheld nerd).
