Let’s remember that the Oscars are not purely restricted to American productions. You could triple the depth of Little Nemo’s list by including Japanese anime…
But it would have to be anime that meets the Academy requirements for eligibility.
For Best Animated Feature, here are the relevant rules:
First, it must meet the general eligibility requirements of all films (primarily it must be exhibited in 35mm or 70mm format or a non-video tape digital process and it must be exhibited for at least 7 days in Los Angeles County during the appropriate year). As near as I can tell, for a Japanese animated film to be nominated in this category would have to meet these requirements rather than the Best Foreign Language Film requirements
An animated feature is defined as being at least 70 minutes long, with a significant number of major characters being animated. Animation must figure into at least 75% of the pictures running time.
So, Episode One and Mary Poppins would not qualify because their major characters were not animated. Who Framed Roger Rabbit probably would qualify.
Also, Academy Rule 07, paragraph 7 explicitly states that “[f]ilms submitted in the Best Animated Feature Film category may qualify for Academy Awards in other areas, including Best Picture, provided they meet the rules criteria governing those categories.”
So, the problem with considering anime is that very few such films would qualify for eligibility as few are ever exhibited commercially in the United States.
Feel free to fill in any blank spots on my list. But as obfusciatrist pointed out, even with anime it’s difficult to find animated feature films which had a theatrical release. As it is, I wouldn’t want to be the one that had to vouchsafe Faust, Perfect Blue, or for that matter The Tune as having been released theatrically.