He wrote a graphical toolkit, a sound synthesiser, an HTML parser, html template language, a language (grammar, parser, vm and jit, gc, ...), and many other software projects on his own.

All of these are a joy to use. They are not only well though out technically (and it's an euphemisim), their APIs are excellent and often fun to use, and they are wonderfully documented.

Do you know of many people who are proficient in so many domains?

He also has a very personal graphic and literary style. What makes him unique is that he treated coding as an artistic medium too, and that he was able to mix his various skills to create integrated works.

Can you name somebody else that would qualify for these traits?

If not he's indeed a remarkably unique artist/hacker, and a creative visionary since no one had done that before.

No, taste is subjective. That _why is unique, a hacker, an artist and creative is not.

"And I was claiming to be an outsider to the Ruby community"

Yeah, hence why I'm highlighting the inanity of your insistence on viewing his work through the prism of "Ruby" rather than for what it is: creative code in multiple languages including one he invented, artwork, music, books and commentary on making programming more accessible and fun.