Wow..great thread topic!
Where to begin....there are so many "overlooked" and "underrated" films it's hard to remember them all!
I would have to say that Treasure Planet was absolutely stunning and very well done. I don't understand why it was labeled a "failure" during it's release and then quickly forgotten. The character animation was stunning and the vocal performances, backgrounds, and exspecially the film score was top notch. Wow...what a spectacle! Add to that a engrossing story, and some heartfelt meaningful moments and it's a win/win from the start.....at least for me it was. Maybe i see these films differently then your average movie goer. As a serious animation fan i see everything...things that the general public might not even be paying attention to ( like the backdrops or score maybe?) I don't know...but this movie was GREAT!
The Rescuers Down Under was another great movie. The animation was excellent and the sweeping music lent itself perfectly to the incredible fully immersive shots ( your could tell CGI was the "new trick"). Wilbur could get annoying, but the villians and Jake more then made up for it. Another winner...sadly "underrated" simply because it came out the year after "Mermaid" and the general public was expecting another fairy tale musical. I'm sure if "RDU" came out BEFORE "Mermaid" it would have been a smash, riding off the then hot animation trend thanks to the previous years release of "Roger Rabbit". Too bad "RDU" never had that shot.
"Robin Hood" is another gem...i will admit that i do not care in general for the "later" Disney animations that were released in the 60's ( Aristocats, Dalmations, etc.) but Robin Hood is the exception. What a CLASSIC!! Prince John and Sir Hiss absolutely make this movie...and the Sheriff of Nottingham is great too....so many great characters!! I rememeber buying this on video back in the late 80's and not expecting much..but wow was i deleightfully surprised at what i experienced. Another great movie well worth checking out!
Does "Pete's Dragon" count as a "underrated" film? I adore this movie...it was a favorite of mine as a child and i still love it now even more then i did then. Again, some great characters and fantastic music make this movie a winner. Jim Dale is awesome as Doc Terminus and the clever stunts they pull with the early style of animation/live action sequences for Elliot are very fun. I LOVE this movie!!!
Ah, "Oliver and Company". I don't regard this as a huge fave but it's still a good movie. Tito and Dodger are great, and Bette Midler as the posh poodle is priceless beyond words. I always liked this movie, so i should add it to the list of decent wonders.
"Hunchback" was awesome too...but i can see why it was not the huge success everyone was hoping for. I think for the time of it's release, some of the subject matter turned off a lot of parents of the little kiddies. Some scenes that involved Frollo and Esmerelda togther had a LOT going on in them (wink wink) that certainly raised more then a few eyebrows in the theatres. It's a shame everyone then had to dwell on the negative aspects because in reality the film had a extremly positive message and some charming characters. I have often regarded this movie as "Adult Disney" animation....not something for the kiddies. Was this rated pg? I don't rememeber...if it was'nt, it SHOULD have been! I love this movie and watch it a lot...i loved the attractions they used to have in the Parks too that were related to it ( Hunchback stage show being one of the best)...shame to see these dissapear over the years.
How about "The Black Cauldron"? Nobody, and i mean NOBODY ever talks about this movie! Sure it's considered poor grade to today's animation standards ..... or at least it looks poor grade. I have the video release and the impression i get from watching it is that little care and effort went into it's transfer...the film print is all wasked out and terrrible! Seeing it new in the theatre, in 60mm was awe inspiring...wow it was COOL...and i personally loved the "dark" turn Disney tried out with this film. Again, not one i can see parents taking there toddlers too( thus the main reason it failed at the box office in 1985)..but definately something older kids and even teens could dig. Gurgi was a gem too....and the Horned King along with Creeper were fantastic! Another movie i like a lot!
"Dinosaur" was very well done too....does this count as a "underrated" film? I know it's a CGI film but it's still under the Disney banner somewhat. Another film i like a lot...i don't know why this was'nt a huge hit either. It has everything going for it....maybe there was too much talk for the kiddies? I don't know...but from a visual standpoint it wads stunning. The music is awesome too...it really adds to the story. Great, great stuff!
WEll, that all i can think of now...time for someone else to list some! If i rememeber any more, i will mention them.
With "Go the Distance" being an all time favorite song (Just not that HORRENDOUS rendition by Michael Bolton. :hurl: What were they thinking?!) 
