As far as theme and atmospere effectiveness, I still get the creeps waiting outside, entering the doorway, and every detail afterwards until I sit down in one of the cars of the Haunted Mansion. Still spooky at night to.
However, I have to give it to the designer of the Tower of Terror hands-down. From the time you enter the garden walkway ramp, wind through the grounds, and enter the lobby. It's gorgeous and I can't imagine how much they spent minus the actual elevator ride equipment. The details are amazing.
I have placed my vote for Pirates of the Carribbean as well. I was reading the other day about some of the detail they put into it. For instance, when walking through the line, there is somepoint where you can see two skeletons in a cell, forever locked in a chess match. The cool thing and super attention to detail is that the chess board is set up so that the remaining peices can only move in ways that will result in a tie! Thus you get to imagine how that played out for the prisoners.
I think for me it has got to be the Haunted Mansion and I include the stretching room as part of the load area since it happens before boarding a doom-buggie. Genius!
Also, It's Tough To Be A But is surprisingly wonderful and really makes you feel like you're becoming a bug, entering their world.
I do find it interesting that very few people if any list EE as their fave. It's so elaborate and detailed but somehow it doesn't seem to resonate with people. Is it because it's too serious? The Yeti research and museum isn't believable? Just curious!
For me, my overall favourite load and unload goes to Journey into Imagination. The mural at the original load pictoring every part of the story, then the unload system and how it cleverly got guests into the Imageworks and the Magic Eye Theatre.