Nintendo DS games, go on, start listing names, seeing as i just got me a DS.

PLURAL, not singular dammit

Mario Kart DS
Super Mario 64 DS
New Super Mario Bros
Pheonix Right Ace Atourney

There's a few decent games from the top of my head.

Advance Wars: Dual Strike
I'll include some more later; that is the one that comes to my head that others haven't already suggested.

Metroid Prime Hunters
Henry Hatsworth and the Puzzling Adventure (tis lol)

Proffesor Layton and the Curious Village
+1 to Pheonix Wright
Piccross (or Picross?)
Tetris DS (surprisingly good)

Thats all I can think of for now. I'll edit/repost if I think of anything else.

Advance Wars - Dark Conflict is also pretty good if you're into that

Errrm... Dunno what sort of games you like Mario and Sonic @ The Olympics is cool, MKDS is win aswell xD

RPGs mainly. Sidescrollers as well.

CS:DS !!!

if I had one I would say advance wars and mario kart because they are ftw ^^

Final Fantasy Tactics DS might be your sort of thing... I dont know I only own like... 5 DS games, 3 of which are Pokemon XD

Final Fantasy tactics is very good i feel but other games drag me away. It is a turn based game that i feel only just scraps being repetitive of fighting by its many varied and seasonal quests and intriging main storyline. Classes are very varied as are the armour, weapon, accessories and them the skill sets as well to perfect your perfect team.
I do like it for long journeys especially as i seem to find somethign to try and do even if it's just levelling a bit or looking for that one chocobo for my chocobo knight.

Playing pheonix wright now, it starts off slow but is very good and after you learn the way the game plays it seems to throw more features at you and is very interesting and fun puzzle and theory game .

Advance wars is very good story and style strategy game but i feel it need friend play to live past the story mode in my opinion. i'll add more in a bit after L4D

For sidescrolling, Henry Hatsworth is pretty good, has a puzzle element aswell (worth looking up first).