Sergio, not to be rude, but it's a good idea to look around a bunch before making assumptions about a place. If you look at some of the topics we've discussed in the past month, they include such things as "What's the best book?" which is clearly not a music-related thing. We discuss a lot of stuff. Our love of folk/blues music brought us here, but it's not the only thing we talk about.
I think my answer to your new, improved question would be exactly the same. I assume you're talking about performance artists and not composers? If both fall into the provenance of the question then the problem is even worse. But even if it's only performers, the question is too diverse. Who's better, Glenn Gould or Jimi Hendrix? The question is still meaningless. You can't compare a pianist with an electric guitar player. But even in one instrument, how can you compare people whose styles are wildly divergent? Who's better, Doc Watson, or Mississippi John Hurt? Meaningless.
Say we just look at vocalists. Who's better, Luciano Pavarotti, or Jean Redpath? Again, meaningless.
I'm sorry, but no matter how I slice your question, I can't make it a meaningful one.
On the other hand, "Who is your favorite artist?" is quite a meaningful question, and perhaps it's the one you wanted to ask?
To Little Hawk: This refers to the book/series, "The Hitchhiker's Guide to the Galaxy." A computer is programmed to come up with "the answer to the ultimate question of Life, the Universe, and Everything." It gives "42" as the answer, and then suggests that the question was a little vague, and they didn't say (and don't really know) what The Ultimate Question is. So they create another computer to come up with the Question. This computer is sometimes mistaken for a planet, viz., the Earth.
It's a very fun romp, and the best way to enjoy it (IMHO) is the radio series (which came before either the books or the (hideous) video series).