The DS CastleVania games are all pretty good, and Symphony of the Night is one of the greatest 2D games I've ever played.  Besides, many 2D to 3D games made horrible conversions (Mega Man and Contra, to name a few.)  That's why it baffles me to this day how Mario and Link jumped the generation gap with such style in the late 90s.

You forget the horror of BomberMan Act=Zero. All three of those franchises have had trouble with it's gameplay being adapted outside for their traditional 2D roots.

If I would choose one of those franchises, it has to be Castlevania, no contest. I'm not even a hardcore Castlevania fan, but the series has truly flourished on the DS. It's a type of success you can ignore.

The new Sonic Unleashed seems to be a step in the right direction. Not so much liking the "wolf sonic" thing.

I would go with Sonic and the Tony Hawk series.

Dawn of Sorrow and Portrait of Ruin were fantastic games though. And Order of Ecclesia looks awesome. No, I don't agree that those franchises have gone sour at all. I do agree that it's a shame there's no way to break that formula into the 3D realm, but that's only keeping the franchise off consoles and on handhelds where it's made a very nice home for itself

I think a lot of people will say Bomberman and with much reason to. Bomberman was originally known as a cool great 4 player game where you blew up your friends with bombs, then it totally went left field crazy and tried to be so many things it wasn't. It started with crappy RPG Bomberman attempts that I kinda enjoyed at the time cause the power ups to Bomberman's bombs were just permanent. Then it just all went downhill when they decided to make crappy party games and dumb futuristic Bomberman!.

Runner ups are of course: Castlevania, and Sonic. I think these Franchises are really just hurt by the fact that there really is no way to evovle them. Keeping them 2d is always great but when you do they do that they never innovate and people who like 2d games are few and far between now a days!