It would seem this one is eluding us on RB's awesome list of Hidden Gems. Maybe we can help him out a bit?
I'd say Monster Max is THE hidden gem of the GB era and whilst a huge franchise, Pokemon Puzzle League is an often overlooked little sister to the killer app RPGs.
I've talked with Racketboy about this before and he said the list is quite comprehensive so he didn't want to rush it. That was awhile back though... I wonder where it is... I always had fun playing Crash Test Dummies. Not sure if that game is considered a Hidden Gem though.
Aice in Wonderland is one of the most beautiful platformers for the console. Great Greed is one of the best RPGs.
And Bionic Commando really showed what a good sequel needed to be.
I am all for a Gameboy Article, I may have to contact Racket about this and see where it is...
I did some searches in the Nintendo section for Gameboy or Game Boy (can't remember which) and had it only return threads that included Gameboy (or Game Boy) in the title of the tread, and I found a few with people already having this discussion.
Final Fantasy Adventure was remade on the GBA under its proper title Sword of Mana. It took the Graphics of 3, the gameplay of 2 and remade 1 - now thats not a convoluted sentence: http://en.wikipedia.org/wiki/Sword_of_mana