I found DKC1 really bland on my first play of it two years ago. Bland/bad looking environments, none of the cool flair of DKC2. The music was just OK too.
Actually those complaints apply to DKC3 as well, except DKC3 was worse off because of Kiddy and really fricking annoying level gimmicks (I have an idea, let's reverse left and right on the controller!) and bosses (snowman fight... ugh.) It also went a bit overboard with collectables, closer to DK64 in that respect than DKC2.
Naturally, the whole trilogy will never be in the top echelon (for me) because of the spotty collision detection caused by the "3D" graphics. DKC2 rises from "mediocre" to "very good, entertaining, and memorable" on the strengths of its level design (which is actually quite good), area variety, pleasurable level gimmicks and gameplay mechanics (like the spider), and, of course, music.