Movie-length Anime, Best to Worst:

The length of a movie and a pint-sized anime series (shorter than 4 hours) are basically the same, so the two should be treated as equivalent formats.  Short works like these can't be compared to longer epics, anime that comes in the 4 hours and above format, because no matter how well done a short story is it's still too short to compete with vaster worlds, more complicated plots, more characters, deeper characterization, longer timelines, etc., etc.  It's an unfair and hopeless contest, short stories do not belong on the big stage of 'Top Anime Rankings.'  That's where the big boys go to compete.  So where do the little people fit in?  They should be compared to their direct competitors, live-action and CG films, who share the same time constraints.  They fit in the 'good movies' hall of fame, because that's what they are.  A bunch of good anime movies.

With that framing in mind, these are the 21 best movie-length anime, from best to worst (even the worst is among the best 200 movies ever made so is still receiving a great honor here):

1. Tokyo Magnitude 8.0

2. Negima! Ala Alba + Magic World oav's + UQ Holder's oav's

3. Battle Athletes Oav's

4. Gunbuster

5. Kiki's Delivery Service

6. Summer Wars

7. In this Corner of the World

8. Mononoke Hime

9. Spirited Away

10. Fatal Fury

11. Shamanic Princess

12. Binbou Shimai Monogatari

13. Read or Die Oav's

14. Suzume no Tojimari

15. Nausicaa of the Valley of the Wind

16. Omoi, Omoware, Furi, Furare

17. Planetarian

18. Grave of the Fireflies

19. RG Veda

20. Futari Ecchi

21. Alien Nine

#1 Tokyo Magnitude 8.0 benefits from being 11 episodes long, so the longest possible while still qualifying for this category, i.e., the big fish in the little pond.

Negima and its sequel UQ Holder have many episodes but they're all filler-plagued save for the Ala Alba and Magic World oav's of Negima and the three oav's of UQ Holder.  These oav's can be stitched together to form an eleven episode canon, which is within the movie-length threshold.  Though even these episodes abridge a lot of content at least what they do show is all faithful to the source.  When you have such a great source work to draw upon and show some of the coolest scenes from that source work it ends up as the 2nd best movie-length anime.

After that the lengths are all about the same; Whether it's a 6 episode ova or a single movie, it's a level playing ground.  From here it comes down to pure quality of story telling, as all these shows are trying to squeeze in as much stuff in as little time as possible.

Some of these stories leave off on cliffhangers, others give a satisfying conclusion, and of course that factors into their overall quality, but they all qualify as great, showing that it isn't a fatal error to end on a cliffhanger if the intro is good enough.

Read or Die, Battle Athletes and Gunbuster had sequels, but they were such bad follow-ups to the original, already perfectly well concluded content, that they can only be considered as filler and having no relation to the great movie-length originals.  Thus these three franchises can be considered movie-length.