The most underrated non-Disney animated movies (by critics or by the GP).
Don Bluth is extremely underrated IMO and didn't shy away from dark imagery. He also created some very uplifting female characters before Disney did. He used to animate for Disney, but I guess he felt like he could do more on his own.
Brad Bird's Iron Giant is a gorgeous movie and not as well known as most Disney movies, plus it flopped. It's kinda like ET, but with a robot instead of an squishy alien. Produced by WB.