Yes, we know about Sunman. In addition to the suspiciously similar “original” character, there may be more evidence Sunsoft was developing an unreleased Superman game for the NES.
The Lost Levels came across Famicom Disk System images with prototype Sunsoft games and development tools. Dig through the data disks and you’ll find sprites of a character that looks remarkably similar to Superman.
During the 8-bit days, Sunsoft was a major publisher pulling movie rights for Gremlins 2 and Batman. Sunsoft also had a relationship with DC Comics, at least through the Batman movie, so it isn’t too hard to believe they tried to license the Man of Steel. These sprites may be another look at Sunsoft’s take on Superman.