But yeah, he's generally acknowledged as a really nice guy, and also easy to work with.
Weird Al Yankovic, too, is not generally considered a "great artist". A funny musician who made a career making silly parody songs a few decades ago, sure, but that's not what I'd call a "great artist". Again, not to denigrate his work; it was pretty funny stuff as I recall, but nothing super-amazing.
By contrast, people who are generally considered the very top of their profession frequently have serious personality problems. Kevin Spacey was considered one of the best actors in Hollywood, and look what happened to him. Tom Cruise is generally considered one of the most talented actors of all time, and while he's amazing on-screen, he's a certifiable crackpot and mouthpiece for a dangerous cult. Klaus Kinski was also an extremely talented actor, and also extremely mentally ill and unstable.
And you’re treating Al as a has-been, but his latest album was number one in the US charts.
What exactly makes a “great artist” then? Surely that’s subjective, and popularity isn’t the only metric. We’re talking “great”, not simply “famous”.
But alright, take your pick:
https://www.buzzfeed.com/hannahdobro/nicest-celebs-people-ha...
https://www.quora.com/What-famous-rock-musicians-are-genuine...
https://www.reddit.com/r/popheads/comments/s4rrug/artists_th...
Plenty of names there who are “generally considered the very top of their profession”, and bigger than the ones you picked.
Of course, I guess this could easily veer off into a discussion about what qualifies as "great artist". Does a top-selling musician/singer who has limited range or uses autotune count, or does someone with amazing technical ability but little commercial success not count? Does a "wooden" actor qualify as a "greater artist" if they've grossed higher than Daniel Day Lewis?