1) Click-Clock Wood: Easy number one for me, and honestly one of my favorite levels/worlds in any game. Everything, in my opinion, is topnotch; from the level-design, to the the music and the forest aesthetic.
2) Bubblegloop Swamp: I like the swamp design a lot, and I think the level has a nice variety of challenges and flows well. Plus it has my favorite Mumbo transformation!
3)Treasure Trove Cove: Fun level, that seemed big but isn't too daunting. Great music as well.
1)Glitter Gulch Mine: While it is a confusing place to navigate, I actually really like GGM. The music track is my favorite from the sequel and it's got some cool characters and fun challenges.
2) Witchyworld: I love the run-down amusement park look and the variety of areas that the level has. The music really sells the theme of the worlds as well.
3) Terrydactyland: I know a lot of people don't really like this level, and there's good reason too. The challenges are a little too spread out and there's too much backtracking I think. That being said, I really enjoy the prehistoric theme and I love the T-Rex transformation.
I sadly never played DK64 but Ill give you my top there based on how cool the name is