I'm gonna assume that the topic is meant as "Dragon Ball" as a whole and not just Dragon Ball Z. Here goes, in no particular order:
Advanced Adventure - A really solid and fun 2D platforming beat-'em-up, with a 2D fighting portion. It's basically two good games that complement each other well, making a great game. (Something we never got for the original Dragon Ball since. No, I don't have a Wii so I still haven't played Revenge of King Piccolo.)
Hyper Dimension - Yes, I'm one of those guys

I see Hyper Dimension as the Super DBZ to Super Butoden's Budokai. It tried a new type of sprite visual that I thought worked really well, and it was a traditional 2D fighter with a few twists in the gameplay. It was something new, in the middle of all the card games, rpgs and Super Butoden series, and it was good.
Super Dragon Ball Z - Manga-style visuals like we'd never had before and haven't had since. It was a good fighting game and it was fun to get into. Good character costumization, even down to their attacks and abilities. Kuririn as the best character in the game. Chi-chi with kinto'un, nyoi-bo and the basho fan.
Gohan with the Kaioshin outfit and both his swords.
Infinite World - You could go through the Serpentine Road for the first time in a Dragon Ball game! And explore a place to find a Dragon Ball. You had to catch Bubbles and aim those practise Spirit Bombs at the incoming bricks. You didn't spend more than half the playtime flying from point A to B. And it had the familiar Budokai 3 gameplay, but with the refinements of the Shin Budokai games and without having to rage because of Hyper Mode and Dragon Rush (HD Collection sparked that hate all over again lol). It's the Budokai 4 that some people still ask for.
Sparking! METEOR - Its major flaw was it being advertised (including by fans of it) as "Naw, it's TOTALLY a deep serious fighter, with really unique characters". It's a game where you simulate the actions of the anime and let's you beat other characters up with it. That's all it is. And if that's what you're looking for, this is where it's (still) at.
Attack of the Saiyans - Good, simple, fun RPG. Made good use of all the filler to extend the story. Only flaws: Who the secret boss is; Not having a post-end-game, thus never being able to fully complete the game; LACK OF SEQUEL.
Ultimate Butoden - Really fun fighting. Really fun character costumization. Really fun what-if scenarios. Flaws: NO WESTERN RELEASE or sequel.
Supersonic Warriors - Fun fighting. Interesting what-ifs. Different from every other handheld Dragon Ball game up to that point.
Honorable mentions:
Ultimate Tenkaichi - A good example of what a console Dragon Ball game can/should look like (despite the anime models with manga shading) A reminder that we're probably never gonna get a new game that looks great AND is great, but one or the other.