I've played just about all the major games on the DS that have everyone talking and hyping up the system. But seriously, the one I've enjoyed most must be Advance Wars Dual Strike. Really, this game is just awesome. I played the 1st 2 one the GBA and loved them but this blows them out of the water. Never since Smash bros. have I seen such perfect balance in a game. The depth in CO abilities, units. The well-laid out maps. Yeah, some of the characters may be seen as weird but the story isn't anything to be taken that seriously anyway.

I think I'm beginning to like this series more than Fire Emblem(shudder).

Anyway, what's yours?

Whoops, forgot something, you could add the one which really let you down after high expectations. Mine is definitely MP: Hunters. Controls for the loss. I refuse to touch it anymore. 

I haven't had the DS for long, but Advance Wars Dual Strike was the first thing I thought of when I read your title. Asside from the incredibly stupid dialogue, that game is the gift that keeps on giving.

Age of Empires. If you liked Advance Wars, you will like this -- can potentially drain your entire life...

My hit parade:

Mario Kart DS (it just doesn't get old playing with seven others via WiFi, and I am obsessed with getting every single course and mission with a *** rating so I can see myself playing this game for a long long time - I want to be able to give the game 100% completed to my 3-year old for his 18th birthday)

Advance Wars: Dual Strike (although I'm stuck on a level because I am also obsessed with getting every single mission "perfect" - no casualties - and it's proving to be real hard...)

Dragon Quest: Rocket Slime (finished the main game, but the tank battles are still entertaining and I have yet to complete them all)

Castlevania: Dawn of Sorrow (played through the game twice to get the 100% and bonus endings and whatnot but there's those boss-rush stages that you can always improve on)

Elite Beat Agents (beat the game, but still go back for the tunes and to try to get that elusive "S" rating on Hard Rock mode)

Seems like I have an obsession with getting 100% perfect. Oh well, I am a bit obsessive-compulsive, I guess.

I'm also sure that the list changes every month, but this is it for now...

So far... Pokemon. But I'm thinking by the end of this month it will be Rune Factory.

Pokemon Diamond. 300+ hours and going

I don't have many DS games, still waiting for FFXII: Revenant Wings and DQIX
So far, Mario Kart DS (no. 1) and Advance Wars: Dual Strike (no. 2) combined has used >80% of my DS time.

With Pokemon, I'm playing Pearl since my big brother insisted on playing Diamond. I was about 50 hours into it when my save file somehow got corrupted(really pissed). So I'm about 15 hours into it now. Love it.

Strangely I was replaying EBA just this evening(technically morning) but I don't think its as good as I thought it was. Granted, its fun but it just doesn't feel as instinctive as OUENDAN 2. Man that is another game I'm playing to death.

Mario Kart is always good(Oh MK64, my youth). Phoenix Wright is right up there with Advance Wars though. Finished both about a month ago.

Still haven't finished NSMB. Well that's what you get when you buy about 20 great DS games at a go.

Two must haves. By default, you must own these two. It doesn't matter if they're not your type. They will be after you play the games. It doesn't even matter if you hate Mario. You'll love him after you play the games. If you own a Nintendo DS, you own Mario Kart DS, and New Super Mario Bros. No questions asked. Nobody with a Nintendo DS is allowed to be without these games.

1. Mario Kart DS
2. New Super Mario Bros.

Now, if you're a Zelda fan, you will love The Legend of Zelda: Phantom of the Hourglass. It has been recieving excellent reviews lately. It is a direct sequel to The Legend of Zelda: The Wind Waker.

If you like Sonic, you could buy Sonic Rush, but ever since Sonic left the Sega Dreamcast, he went down fast.

Super Mario 64 DS is another good game, but it's more of a port of Super Mario 64.