I absolutely do not recommend the GBC version of Donkey Kong Country. I got it recently, after seeing many good remarks about how it's such a spot on port and impressive for the system, but then I notice the physics and collision detection are atrocious. So many times have I missed jumps where I've obviously landed on an enemy, only for it to say I was hit by them because the hit boxes are too small. The jumping speed is too fast and has no momentum, and the frog jumps too fast and can't jump while moving forward unless its feet are on the ground, whereas the SNES and GBA versions let you jump while moving forward even if the frog is in mid hop. I've also heard the ostrich glides too slowly in this version as well.
It's clearly a remake based on the Land engine, rather than a port, and has so many issues with it that I got frustrated and bought the GBA version (which I had years ago, but sold when I sold a chunk of my GB collection that I've since bought back). Even though it could have been better, the gameplay is perfectly intact.
And it's not just me:
http://www.youtube.com/watch?v=wdrbGNd4LiA (I know the guy's a bit annoying, but still)