Living in the UK is good as a DS gamer...
you can get most games at ÂŁ22 - 26 if you're prepared to wait 7-14 days for free shipping.
Meteos:
(not my recommendation, I haven't played it but its recommended by others a lot)
Polarium:
Simple puzzle game. It's not something you'll play for tens of hours, that's just not it's nature. It is however something that is a total bitch to master in challenge mode. And there are over 100 puzzles in puzzle mode to go through too. It can send a demo of itself to other DS' including the VS mode. This is ÂŁ20 in the UK -- half the price of a console game in some stores. I strongly suggest you accept nothing but a low price. Ditto for Zoo Keeper if you're considering that (which is basically a fancy Bejeweled).
Yoshi Touch & Go:
This is very good, but again it's not something you'll play constantly.. you'll want to pick it up and have a blast, trying to beat your top score, but I imagine sustained playing would frustrate most people. You start with two modes unlocked - Score Attack and Marathon. Both are quite tough to beat. Levels start with Baby Mario falling from the sky, and you drawing paths of clouds for him to slide down, encasing enemies in bubbles and throwing the rewards at Mario. Depending on how many coins you get in this way determines the speed and egg capacity of your Yoshi. Then you go into side scroller mode. In Marathan mode, this side scrolling stuff lasts forever. Beat the best score in score attack, or travel the greatest amount of yards in Marathon and you'll unlock the other two modes. I can't comment on either because I haven't unlocked them myself yet.
Kirby
I've only seen videos but it looks to be the superior game to Yoshi. And Yoshi has grown on me a lot.
Feel the Magic:
As with the two games above, this game seems made for short blasts too. And if this is turning into a pattern, I don't mean it to sound like a bad thing. It's not necessarily. In addition to this common factor though, Feel the Magic is short anyway. There's lots to unlock but you're basically talking about costumes for your sillhouette girl... not a big deal in other words. The game itself is a collection of mini games, many doing cool things with the DS feature-set... there's even a Space Channel 5 influenced game. It's definately one of the more stylish games on DS, but I'd agree with whoever said get it cheap.
Wario Ware: Touched!
I've had this since February, and let's just say I'm still unlocking things now. I only got the Gold Bear character unlocked the other day, and I still don't have all of the toys. Wario Ware is just one of those games that you can throw on whenever you find yourself in the mood and you still won't know entirely what to expect, or how you'll perform. For whats out now here in the west, its easily one of the better titles.
Wario Ware: Twisted! (GBA)
You'd be playing it on one screen, but I'd strongly recommend this when it comes out here too. And I've only had a little playtime with it myself, yet I'm totally convinced.
Mario 64 DS
Mario 64 is still as good as ever. If you can get to grips with one of the three new control methods, you'll love this too. The mini game collection and new Stars, new character abilities etc. They all add lots of freshness to a game that launched with Nintendo 64 nearly a decade ago. Getting all 150 stars is a total bitch, so if you're looking for something bigger to do inbetween all these quick pick-up-and-play fixes, this is probably the one to get.
Coming down the line, here's what I'm most interested in:
Band Brothers / Jam With The Band -- music game with a good critical response so far
Metroid Prime: Hunters -- DS comes with a Demo, you'll make up your own mind.
Mario Kart DS -- self explanatory.
Animal Crossing DS -- Animal Crossing, if you've never played it before, rules. And this one is online.
Final Fantasy III -- port / remake? I dunno.
Final Fantasy Crystal Chronicles -- this is gonna work perfectly on DS.
The Legend of Zelda: Four Swords DS -- ditto.
Scratch! Viewtiful Joe -- wow.
Wario Ware touched features a Mario Paint minigame. Perhaps I'm reading too much into it, but I read it as a ploy to put the Mario Paint brand firmly back into my conciousness. Mario Paint (or Stage Debut) are bound to come out on DS in some form, under one name or another. When it does, that will be a great DS game.
Add to that the possible benefits it will bestow on Point and Click Adventures, RTS and God simulations and there'll be even more potential there.
I think E3 is gonna have some great things in store for DS.