That is a ridiculous question that does not really deserve any response.
Slayer, Megadeth and Metallica are bands with sellout records, massive mtv airtime and tons of exposure, etc... While not damning in and of itself, it is no surprise to me that I do not enjoy them as much as the more obscure bands that play no holds barred thrash.
I prefer Opeth's earlier albums by far btw. Their appeal to me does not lie in headbangable thrashing brutality or speed, if this is what Metallica, Slayer and Megadeth are trying to achieve they have failed, in my opinion.