This is tough...Horizons from 12 years old made an incredible impression but would it still stand? I recall it being amazing, and I wish my children were able to experience the original Imagination pavilion. But reality is that that's in the past. So the Top 10 attractions that I have experienced with mature eyes:
1. Big Thunder Mountain Railroad (a great but not-too-scary roller coaster with great - needs updating - theming to make it a Disney classic)
2. Haunted Mansion (one of the definitive rides of Classic Disney...spooky and fun)
3. Pirates of the Caribbean (might have topped HM before the Jack Sparrow overlay, but still a classic)
4. Tower of Terror (fun concept and excellent execution. DL version was weak compared with the standard at WDW)
5. Space Mountain at DL (love the idea of SM and it does exist at WDW so it's on here but ours needs to be updated)
5a. if the lists have to be WDW rides, I'll substitute Peoplemover as it embodies Tomorrowland
6. Expedition Everest (thrilling and fun roller coaster...but the cue and theming make it unlike anything else)
7. Spaceship Earth (any version ok...my 7yo loves the lame descent computer thing)
8. Splash Mountain (no explanation needed, but love the Zip-a-dee-do-dah finale once the main ride is complete; a nice finish)
9. Soarin' (probably the original - the new one is good, but the smells of the original made it fantastic)
10. Tom Sawyer's Island (just because it exists)
Honorable mention to American Adventure; we'll go on it next week for the second time since my childhood. I had remembered it as a Top 10, and last year on taking my kids for the first time to experience it, I was no longer so sure. Will reevaluate soon.
And, oh yeah, Frozen Ever After! (is that what it's called?) Just kidding! (maybe - I'll see it next week)