I still think that the hardest level by far is the final Lost World level in DKC3. It took me... about 50 lives to beat. I had to hold my controller upside-down. The whole family got into it, and we even handed off the controller to one another from time to time.
How's that for epic memories?
Fitting way to end the series, I say.
As much as I love about the DKC games, I do have to stop and remind myself that DK learned all his tricks from Mario first. It wasn't until DKC2 that the series really started to feel vastly different from Mario, design-wise.
I notice a lot of people give DKC3 some flak for some reason... sure, it kinda sucked that both DK and Diddy were nowhere to be found, and the environments weren't exactly inspired, but it had it's moments of genius.
The low gravity pipeline
The burning rope
The jungle conveyor ropes
The dark underwater level
The level where you had to feed Nibbla or die
The level where the bees chased you above water
But, of course (and once again!), the best part was probably the music. Sure, DKC2 might have the overall best soundtrack by popular opinion, but DKC3 had some standout awesome tracks too... like the factory theme, anyone? HOW HAS THIS NOT BEEN REMIXED ALEADY?
Also, Mama Bird.