I forgot to mention Testament. Those 3 bands where the cream of thrash. I also forgot to mention Fear factory, they were not thrash or metal, but a hybrid. They kicked butt big time.
I have been a Sabbath fan since 71, a Priest fan since 78 a Saxon fan since 80. They became from that day 80 my holy trinity.
In my view the only 3 bands who could hold their ground with them are Slayer, Megadeth, Motorhead.
Period.!!!!