Mekanos and others went over a lot of this, but there's a little bit of extra flair to the environments in the first game that was mostly ignored by the sequels, like the changing weather and lighting in certain levels. The sequels do it once or twice, but it's never the showpiece it was in levels like Snow Barrel Blast. Though on the other hand, it's also blurrier and more plastic-looking than the sequels, which made great strides with the 3D rendering technology.
As for the music, I guess it like all of the others has its unique qualities. It's the only one to have a meaningful split between two different composers, and I think Eveline Novakovic actually did most of her best work here rather than in 3, so her touch is really evident and important on this one. There's also a more atmospheric bent to it, a lot of themes that have a slow build to them and focus primarily on mood. I think Cave Dweller Concert and DK Island Swing are among the longest level themes in the series, at least prior to Tropical Freeze. Misty Menace notably doesn't really have any clear melody at any point, despite containing repeated phrases. Personally I think it's pretty middle of the pack in the series. It's better than the notably weaker ones, but I prefer all the solo David Wise scores, ironically more for his side of the soundtrack than Eveline's. Aside from a few like Aquatic Ambiance, the themes in this game have never been my favorite work of his.
I'd order the soundtracks:
DKC2 > TF > 3 GBA > DKC1 > 3 SNES > Returns
And yeah in terms of gameplay I've seen people occasionally prefer its more "pure" straightforward platforming. It has less emphasis on throwing items, no team-up throw, no forced animal buddy sections, no crazy types of barrel cannons, almost no levels that go anything but left to right, no real need to collect anything. Though I will say that this in itself is a somewhat rose-tinted view, it's good at this sometimes, but it can get awkward when it tries for levels with a more complicated rhythm than "run and jump straight ahead, never stop", and it has plenty of slower and more cumbersome ones. The water levels in particular are god awful, amazing music aside. Worst stages in the whole series by a landslide, they have no idea what to do with the format at all, and the end of Poison Pond is such malicious bullshit. Generally, if it's outside, it's a good level, and if it's in some sort of cave, it's probably on the weaker side. Although Stop & Go Station, Mine Cart Carnage, and Slipslide Ride are notable exceptions.
DKC2 is actually the only game in the whole series to have a decent character balance. Donkey's advantages are almost never relevant. He runs slower, can't jump as high, and has a larger hitbox in exchange for having an easier time against a few rare enemies that only appear in a few levels. The only times I think there's an actual advantage in using him are Platform Perils and maybe Dumb Drum, Torchlight Trouble, and Elevator Antics. ...And there's the hand slap move, I guess. I usually forget that even exists.
In DKC2, Diddy is still better at pretty much everything, but Dixie has one huge advantage with her hover, which makes her much safer and can even let her pull off certain things Diddy can't. So there's an actual trade-off in picking between the two, unlike all the other games where one Kong is vastly better than the others in almost every situation. Kiddy is mostly a worse Donkey, and Returns and Tropical Freeze belong to Diddy and Dixie (or Funky) respectively.
