Eh, I thought the Ranger games were at least decent. Still, I didn't like them enough to bother purchasing the third one.
I'd say Snap, some people I know really love that game, and I'll never understand why. I found it dull...it's fun for a while, but it gets old after a few hours. That's just me, though.
I can't comment on PokePark, since I don't know anything about it. Mystery Dungeon, Conquest, Colosseum and XD were all good, though not amazing. Revolution at least had acceptable online.