BIG said:
Super Real Mahjong and Magical Drop.
B-
I don't know anything about Mahjong, but the magical drop version for NGPC left me a little empty, I mean the mechanincs are there, and that's cool!, but the game itself isnot colorfull enough, I mean look at bust-a-move, and compare.
All the puzzle games except for Bust-A-Move are very pale in colors, gameplay remains awsome though.
For me the best games in the NGPC, have to be the Card Fighters Series, both are awsome! after that here's a list.
SNK vs Capcom MOTM
Last Blade
Samurai Shodown 1 & 2
KOF R-1 & R-2
Fatal Fury 1st Contact
Gals Fighters
Metal Slug 1st & 2nd
Megaman Power Battles & Fighters (Looks like an NES game on Steroids!)
Neo Turf Masters
Cool Boarders
Cotton (Only flying shooter I have for the NGPC)
Pocket Tennis Color
Bust-A-Move
Pac-Man (Looks so amazing on scroll mode, and plays excellent with the addon)
There are so many more, but I think these are the best ones in no particular order, but if you ask me Fatal Fury 1st Contact is easy to find and plays like Real Bout without the lane switch (unfortunately), but is fantastic nonetheless.