As an afterthought, there is another indicator for relevance (apart from the praise of your peers, which he has got in abundance), and that is whether people will cover your songs.
This hasn't happened a lot yet, and many times he was involved in the recordings, so they're collaborations rather than covers.
My theory on why it's not happening a lot is not because the songs are bad or irrelevant, but simply because the guitar work is so out of this world that you can't possibly interpret it, make it your own in some way. BIA by Sinead O'Connor was maybe an exception, and there are 2 or 3 others, but in many songs it's the combination of the guitar and the vocals that is simply unique.
Same problem with Pink Floyd, Santana and the Eagles: you may copy the songs, and it might sound good, but you can't turn them into your own artistic creation, because the original just sits there like Mt Everest in the background.