Most underrated composer of 20th Century?

Western classical music has always had a heavy European bias, for clear historical reasons. Are the most underrated composers of the 20th century likely to still be mined in those waters?

Mapman is asking the question that - as a person whose interest in classical music is equal parts aesthetic and anthropological - probably interests me more than any other.

I would speculate that increased appreciation of alternative musical languages is probably an inevitable result of the shrinking world around us. I'd also expect that compositions employing microtonal scales (whether from Asia or from Western composers who borrowed the approach) will gain more attention from critics and scholars. The evolution of the legacy of Harry Partch, et al will be interesting to watch.

Similarly, it will be interesting to see how the big names of the second half of the century hold up. Will Phillip Glass end up as the most underrated composer of the century or the most overrated? Which also raises the question of opera and its place in this question. Where does Alban Berg belong?

I'm not really proposing any candidates here, just following up on Mapman's interesting observation.

With regard to the ultimate merits of minimalist music (tho without any suggestion of equivalency and - further - without any personal judgement one way or the other):

I wonder what kind of critique this crew would have provided after the premier of Rite of Spring.

I would have thought it bombastic, if this was about overated Stravinsky would be on my short list.

Not terribly surprising. Your list of overrated music would likely be far more interesting to me than your list of underrated music. But personal preferences differ, I guess, and thus the world continues to go 'round.