Well, I'm very much in the "taste is subjective, there is no good/bad in music" camp, except when it comes to the degree to which a work meets the artists expectations, but here I think there is an element of objectivity. I don't think "influence" makes a good band "great", but I do think that influence is one of those standards that we CAN measure, and it can't be ignored. I think there's something to be said for a band like Van Halen, or Sabbath, or Kiss, or the Velvet Underground that separates them from the Motley Crue's, the Soundgardens or the REMs that come after. Sure, the Velvets weren't that good of players, not even close, but they DID deliver something new, and they DID tap into a zeitgeist like few bands ever have, and that matters. I think if there's no Velvet Underground, there is no Sex Pistols, and if there is no Sex Pistols, there are no REM, U2 (at least as we know them), Seattle (at least Nirvana), Red Hot Chili Peppers, Jane's Addiction, Green Day, etc.