Joe Simon was a writer/artist/editor whose early efforts at Marvel included the Fiery Mask...but we're bound to remember him for ages to come because, with Jack Kirby, he created Captain America! The Simon-Kirby partnership went on for more than a decade, through just about every genre of comics (even creating a new genre - romance comics - together). When they parted ways in the 50s, Kirby went on to bigger and brighter things. Simon? Well, he was still out there, but never really an equal to Kirby again.
Personally, I'm very fond of Simon's 1970s DC comic Prez, which told the story of the USA's first teenaged president and his trials against chess-playing robots and vampires. Even by 70s standards, it was too bizarre to last.
We were fortunate to have Simon around as late as we did (he was 98). The giants of the Golden Age of comic books are slowly passing on...show your appreciation while you still can!