I don't mind Slayer. Musically they have come up with some classic riffs and they get the adrenaline going. The 'singing' on the other hand is a weak link. I prefer thrash with reasonable singing like Metal Church, Anthrax and such like.

Motorhead I have tried (and generally failed) to get into. I like a handful of songs, Killed By Death, Ace Of Spades Iron Horse etc but I can't help feeling there's an element of the emperor's new clothes about them. Lemmy's an intelligent chap, I'm sure he could do better if he tried harder. Three chords over a distorted bassline gets boring fast. And if you listen to the very first album 'On Parole' he can actually sing properly when he wants to.