I don't see any of those bands as being greedy at all. For one, no one becomes a musician not to make money. Show me a musician who doesn't want to sell out every seat in every venue they play, who doesn't want to sell millions of records or who doesn't want to try new things in order to remain musically relevant, and I'll show you a teenager who DOESN'T tug one out any time the parents are out for the night. Such a thing doesn't exist.
All that said, I don't blame bands like Megadeth, Slayer and Metallica for mixing it up and trying new things. It can get pretty damned boring playing the same songs over and over for 30 + years, so why fault them for trying something different? If you like it, great. If not, there's no federal statute saying you have to listen to it.
But you know what really irritates me? When a fan says “Oh, such and such band sucks now,” so the band heeds their fans and tries to produce something in their old style, only for said fan to accuse them of being dried up and unable to come up with something new. I say, if said fan thinks they can do better, they should put their money where their mouth is. Keeping in mind, of course, that those who can, do; those who can't, criticize.
Incidentally, I loved Load. And I thought Reload had some quality stuff, as well.
