I believe they still are. Thousands of people still go to their concerts, so it's not like they are irrelevant. It's not because you don't like metal or hard rock that you should take conclusions like that.
How many people go to concerts of actual bands?
I recently went to the concert of the Big 4 in France (Sonisphere Festival -
http://fr.sonispherefestivals.com/) and there were 120.000 people there. I had a great time.
oh, I see....you're from Europe, which would explain why you think they're relevant.
Like The Rolling Stones and The Who are "relevant" ....uh...because they're still touring or something.
The last time any of those four bands were spearheading their genre or had mass appeal, was when the black album hit. Which also marked the last worthwhile contribution that Metallica had.
If you consider what made Metallica great, it was by-in-large Dave Mustain's contributions to propel them into such a heavy fucking band. So that would muddy the waters over picking Metallica over Megadeth
Cliff Burton didn't hurt,either. For as much grief as his replacement got, "...and justice for all" was probably the heaviest (new metal) sound they ever got. What has Metallica done in that 20 year period? A lot of remixed, shitty retread garage days, and i-don't-know-what-the-fuck-this-is with Death Magnetic and St.Anger. Those were colossal piles of shit.
I've been playing guitar for 30 years with a lot of different bands. I've played the Metallica/Megadeth stuff.....the thing was, I learned how to turn a fucking page on a calendar. Fuck, people leave the past in the past
Want some real heavy fucking metal (not much of a fan anymore), but Sepultura(and its many machinations), SOD, and Rage are where these "big 4" should've evolved to