I have a few favourites but I've been a fan of Metallica the longest. I also really like Otep.
Well I make this choice now by asking myself which band has produced the most amount of consistently good music and the least amount of songs that I do not like. I don't think I have heard even one Metallica song that I genuinely don't like. There are soooo many good metal/hard rock bands but there is no doubt in my mind that overall Metallica rule.:-)
True, their particular style is who they are. The bands who stay true to their style seem to last. Like Iron Maiden or even the Rolling Stones. They are unique and have set certain standards that their fans have grown used to and will always enjoy. Rock on !