Monster Hunter is all capcom needs to release and I'll be happy, so that's my bias. Konami's GB output was impeccable though. Tragic how that's made a turn.
Not quite impeccable.
They were
superb at the start. Bad n Rad, Turtles 1 and 2, Belmont's Revenge, Contra, Nemesis 1 and 2, - even the first Castlevania Adventure, while it had control and balance issues, had the best graphics on the platform at release, and a fantastic soundtrack.
After the Pokemon GB renaissance there were a few lower quality KCE Nagoya releases. Castlevania Legends, for example, is a far lower quality game than Belmont's Revenge, in graphics, music, everything. The Contra Spirits port by Factor 5 is western jank. Their GBC work was spotty too, though Crazy Bikers (Motocross Maniacs 2) was an amazing little gem.
GBA was a mix too. Even just looking at Castlevania, Circle of the Moon is solid, Harmony of Dissonance is a garish mess, and Aria is great. The Contra game is a total mess, smashing the low colour bleugh of Hard Corps levels into Contra Spirits.