It has nothing to do with them coming from the sixties (I suspect for a few bands/artists it has something to do with them growing up as kids in post WWII times, but that's another discussion), it's to do with the body of work they created. That's what defines greatness, not when they were around, or how many people sing their praise. It's about the music they made.

What makes those older artists that you mentioned more talented than any current band?

The breadth, quality and consistency of their work. They'd put down an amazing album, and do it again, and again, and again, with few exceptions.

And we still see people doing this today, just not any of the big names.

I guess this will just go to opinion but I mean Hendrix only put out 3 albums, I only consider 2 (maybe 3) Beatles albums "great", 1 great Led Zep album, 1 (or 2) great Stones albums, etc. There are numerous 00s bands that id consider having put out more consistently great albums than them.

And Nirvana and the Sex Pistols were brought up earlier too. Not much consistency there either.

One only great Zeppelin album? Assuming you mean LZ4?

I think all of their first six are great.

Nah II is my favorite. Actually III and Houses of the Holy are really good too so they could be fringe greats. Never been huge on IV tbh but its still probably better than Physical Graffiti or I.

I think it's pretty hard to argue against Radiohead in terms of consistency, reviving musical interests, and experimenting with popular sounds. Even in their experimentation they're validating popular forms. If you want to argue it's not "rock" enough I think we're narrowing the focus too much for a discussion of modern popular music. I really don't buy that we can only have greats from Nirvana on back; Radiohead have had a huge contribution and have had more albums AND have practically as consistent, especially considering they're still ongoing.

Actually Z4 is not as good as their first three.

And I like new music as well as older, but I have not yet heard any newer artists that could be better than The Fab Four.
But maybe it is just because they were indeed Fad and someone has to be the best anyway.
But those who say that some new artists, as good as they are, are as talented as, for example, Beatles, I would be thankful if you mentioned some names. If there is such great music, then I wanna know about it too.
But, though, these things are always subjective.