My favorite composer is Alan Silvestri. There's just something deeply magical about 'Back to the Future' score.
However, John Williams is indeed amazing, he has the 'cosmic touch' - I am sure he was able to channel something divine from the Cosmos through him into his music back in the day (no one seems to be able to do that anymore, though).
Not all of his songs are that great, Jurassic Park, for example, feels like just reheating the old coffee instead of something fresh and inspiring. It's still pleasant and good-ish, but not 'magical', compared to what the Superman score is.
Even E.T. score has amazing melody and very deeply moving structure - not a cliché-ridden, forced heartstring-tugging, that's easy to do, but something that goes beyond the heart into the higher levels of existence through your soul.
However, to say 'who ever lived' is quite the stretch - how can you know what kind of composers lived in Atlantis? How can you know what kind of composers have 'ever' (a long time) lived on other planets/spaceships? Also, 'ever lived' also means 'every dimension in existence', and the _whole_ history of all existence of the whole, incredibly vast Universe with incredibly impossible amount of galaxies.
I am not saying you can't know these things, I am just wondering.. HOW you can.. (I'd like to reach that kind of omniscient ability to know so much about other-worldly existence as well).
What a COINCIDENCE, that the BEST composer who EVER lived (are you saying there are dead ones?) just happened to be incarnated on THIS planet of all planets, THIS age of all ages, and no other composer ever reached, even through billions of years of history, his level of composure.
Now, THAT's even more amazing than anything these people composed..