Well, I personally love the first BTTF movie, but the other sequels were lame. Also, I just had a chance to ride the new Simpsons attraction that replaced BTTF, and it was excellent. Finally, BTTF broke down so often that waiting in line ate up a good chunk of time, so a replacement and update was necessary.
Alien Encounter was not based on any attraction, so it was timeless. Also, the attraction that replaced it was the extremely mediocre Stitch. Finally, Alien Encounter was something new for Disney - an attraction aimed at teens/young adults. It's unfortunate that they listened to the parents who ignored the warnings and brought their children on rather than the throngs of people who got a real kick out of the ride. I mean, it must have been good if it made it to the extinct attractions' finals.
It's funny that the tournament came down to two attractions that weren't demolished, but rejuvenated. The original ride systems remain intact and only the presentation varies.
Both great rides, but BTTF was simply a simulator (granted it was easily the best simulator in O-town), but still, not that innovative...
I voted for BttF because I never liked ExtraTERRORestrial Alien Encounter. And I'm a fan of the BttF Trilogy. And I could care less what replaced each attraction. Sure, many people hate the Stitch version, but I don't enjoy the whole concept of the attraction.
I'll agree though that BttF was beginning to show its age by the late 90's just due to wear and tear.