the world ends with you

castlevania Dawn of Sorrow + order of ecclesia

SMT - Devil survivor is looking good

FFTA2 - GotR

Puzzle Quest: challenge of the warlord

and if you havn't played them

Chrono Trigger

Final fantasy IV

from GBA off the to of my head

Riviera: The Promised Land

Golden Sun 1 +2

I would say, only buy a DS Lite if you are interested in GBA games or want to save $40.

Some recommendations:

Action Adventure:
Castlevania: Dawn of Sorrow (or one of two other Castlevanias)
GTA: Chinatown Wars
The Legend of Zelda: Phantom Hourglass

Adventure:
Broken Sword: The Shadow of the Templars - Directors Cut
Hotel Dusk: Room 215
Phoenix Wright: Ace Attorney (3 other from the Ace Attorney series currently avaiable)
Professor Layton and the Curious Village

Building Sim:
Anno 1701: Dawn of Discovery (or Anno: Create A New World)
SimCity Creator (or SimCity DS)

Strategy (turn based):
Age of Empires: The Age of Kings (or Age of Mythologies)
Advance Wars: Dual Strike (or
Sid Meier's Civilization

Strategy RPG (real time)
Final Fantasy XII: Revenant Wings

Strategy RPG:
Fire Emblem: Shadow Dragon
Disgaea DS
Final Fantasy Tactics A2: Grimoire of the Rift

RPG:
Chrono Trigger
Dragon Quest IV: Chapters of the Chosen
Dragon Quest V: Hand of the Heavenly Bride
Final Fantasy III
Final Fantasy IV
Mario and Luigi: Partners in Time
Suikoden Tierkreis

Puzzle, Card/Board:
Puzzle Quest: Challenge of the Warlord
Planet Puzzle League
Tetris DS
Clubhouse Games (aka 42 All-Time Classics)
Meteos

Other:
Elite Beat Agents
Soul Bubbles

Most interesting upcoming games:
Scribblenauts (September)
Professor Layton and Pandora's Box (September)
Mario & Luigi: Bowser's Inside Story (October)
The Legend of Zelda: Spirit Tracks (December)
Golden Sun DS (this won't come in the near future)

All VGChartz DS reviews
http://www.vgchartz.com/games/index.php?name=&keyword=&console=DS&region=All&developer=&publisher=&genre=&boxart=Both&results=50&order=Score

VGChartz DS RPG reviews
http://www.vgchartz.com/games/index.php?name=&keyword=&console=DS&region=All&developer=&publisher=&genre=RPG&boxart=Both&results=50&order=Score

Elite Beat Agents is supposed to be good. And Scribblenauts is coming out.

Buy a Dsi because it'll get some excluesive features as well as a inernet browser and the Dsi shop which in the future will get way better games. So the dsi is better in the long run.
As for games new super mario bros kirby super star ultra and the lengendary starfy

Yes.

Get a DSi not a DSL. Yes you lose out on compatibility and an old library of games; which you the OP has ignoref because clearly the GBA didn't appeal to you previously. If you get a DSi you won't get stuck with just the backwards games. The DSi does have more RAM and apx double CPU speed. While most games now will be for the DS it is assured that sooner or later there will be a DSi games. If you bought the DSL then you would need to upgrade to the DSi.

As for the games themselves. There is lots' of RPG games out there. Lots and Lots of them.

I don't think Nintendo would drop the 80M+ install base of the DSL just to add more features. DSiWare games, yes, but major DS titles are likely to have DSi-only features rather than exclude the whole market.

The OP missed out on a lot of great GBA games - how can you say he didn't like them if he never tried them? Anyone who has an interest in Mario Kart and Zelda is going to like a lot of their other first party titles [of which there were very few on the GB but a lot on the GBA].

I still have my GBA around, so I'm looking into upgrading my DSL to a DSi when I have the money. From what I see, if you really want to play the GBA games, here in the States, it seems GBAs could be had for $15-20 and the GBASP for $40, so I might suggest seeing what you'd have to pay for a GBA if you want to play its games. I also assume that the DSi still gets its 1000 free points for logging into the shop channel in the UK (I assume that's where you are because of your profile). If so, that kind of makes it $10 lower priced, which might be half or over half the cost of a GBA.

IMO, you can skip the GBA entirely as there's a massive amount of games on DS that you'll never have enough time to play them all.

Plus, there are/will be downloadable games and stuff for DSi.

You can probably get a GBA for $30 on ebay?

if you want to also play the gameboy advance i recommend the ds lite if not the dsi.