I never played the Donkey Kong Land games and gave them a spin last night - quite impressive for Game Boy games. The animations are smooth and it almost plays like the SNES versions.
Naturally the issue comes with the narrow view of the levels and sometimes it can be difficult to tell if you're landing on a platform or if it is something that is part of the background.
Yeah, I have the first one on Game Boy and while they're quite impressive on a technical level, it's really hard to play (particularly on original Game Boy without any color help).