Top 5 Imaginative Films

5. Eternal Sunshine of the Spotless Mind
(Michel Gondry, 2004)

4. Back to the Future
(Robert Zemeckis, 1985)

3. The Fifth Element
(Luc Besson, 1997)

2. The Matrix
(Andy & Lana Wachowski, 1999)

1. E.T. the Extra-Terrestrial
(Steven Spielberg, 1982)

Honorable Mentions:

2001: A Space Odyssey - A must mention, but it would be a cop-out to have it on the actual Top 5. 
Pan's Labyrinth
The Cell - An underrated film
Inception
Avatar
What Dreams May Come