I've recently come to concede that Reign in Blood is Slayer's finest moment. With a couple of stipulations.
1) Show No Mercy comes, very, very, close to matching it in quality.
2) Greatest metal album of all time? No.
3) Most certainly does not excuse Slayer for all the awful trend hoping they did from 1995-2005.
He's like "yo give me yo insurance information!" and I'm like "I didn't hit you with no car, I hit you with this mack truck I call a fist!"