The difference between the other 3 artist on this list and Jeff Buckley, is that Marley, Drake, and Hendrix had achieved legendary status prior to their death (well, perhaps not Drake, but he was certainly much further along than Buckley was at the time of his death.)
I disagree completely. At the time of his death Buckley had released one amazing, yet comparatively unknown album. It's hard to speculate on Sketches for my Sweetheart the Drunk. I think it would have been a great and much more refined album than what we have of it now, but nowhere near the quality of Grace. Grace was a sleeper album, and I can honestly say that I definitely did my share in spreading it's gospel shortly after it was released, however I don't think that the quality of Grace as an album is an infallible indicator that Buckley's status would be anywhere near what it would be if he hadn't succurabed to such an untimely death. Quite the opposite, I think it was his death which set into momentum his future legendary status. I also believe that had he lived we wouldn't even be talking about him right now, and this is coming from a huge fan.