Any musician or band changes their sound over time. Metallica is old, they've been around 20 plus years. Of course over that time frame their sound is going to change as they mature as musicians. Do I think they suck now, yes. But that's besides the point. I stopped listening after the release of the black album. But if I were put in their shoes I would've done the same thing. It's the old adage, the rich only want to get richer. And that's just what they did. I don't really think they tried to get onto MTV and "sell out," I think that everyone started to change their attitude about that type of music. And it continues to this day. 15 years ago, MTV would have never even dared to play System of a Down. Now you can turn on TRL and see them on the countdown. Did System of a Down sell out, or have people accepted the fact that the public likes that kind of music? I think it's the latter. Once the public started to accept them, it began to spread from their hardcore fans (Kill 'em All) to people jumping on the band wagon (Black Album, in specific, "Enter Sandman"). So to call them "sell outs" is just ignorant.
About that "theeshredder" dude, people try to be like their "heroes" because that's usually what inspires people to pick up a guitar. There is nothing wrong with trying to imitate a legend, that's how different styles are born. You probably picked up a guitar after listening to different songs and deciding "Hey that would be cool if I could play that" and all of the sudden you're playing guitar for 10 or 15 years.
Ahh well....life goes on...
Sometimes I hit notes only dogs can hear.