I'd give it to Capcom for the SNES, but I think that in terms of point-to-point-bang-for-buckness Konami takes the NES. Greater variety with overall quality within said variety. I initially wanted to say Capcom but I don't think that's true after some thought. I also initially went to Mega Man vs Castlevania, but they're not particularly comparable, if you ask me. Yeah, they're both platformers, but the approach, the atmosphere, and the mechanics are different enough that they each have tremendous strengths and weaknesses that make them distinct from one another.
This got me thinking about Mega Man vs. Castlevania, and I feel like each series produced two great games on the NES, despite the fact that Mega Man had twice as many tries at it.
Also they both peaked at three, but one company kind of knew when to say when (though MM 4-6 are certainly playable games).