Ooh, another list I haven't done yet....Though it oddly feels as if I have.
Here's my current 10, in no particular order:
Elvis Presley
Elvis Costello
Frank Sinatra
Simon & Garfunkel (including Paul Simon solo stuff)
The Beatles (inc solo ventures. Well, maybe apart from Ringo).
Dusty Springfield
Marvin Gaye
Smokey Robinson (as a songwriter as well as performer - he penned more Motown classic than you'd think)
Johnny Cash
...and leaving the most contraversial to last...
Adam Ant.
Clare Newsome is Editor-in-Chief of What Hi-fi? Sound and Vision