I'm not even that much of a Disney fan, but their castle logo is probably my favorite. The one that starts in the clouds and pans down past the train in the distance.
Surely you don't mean the late-'90s one that debuted with The Lost World: Jurassic Park? I rejoiced when that eye poison was replaced for the 100th anniversary.
Worst is Dreamworks with that super-annoying boy fishing. Horrible pseudo-"romantic" theme. Has Spielberg come up with that idea or what. Also, that Universal logo that looked like a nuclear war outbreak.
As several of the previous posters, I like the current Disney logo best. Great look and full of details. I also always thought that incorporating a film reel somehow is fitting nicely. Constantin Film's logo does this.