If you like George Thorogood, you need to listen to John Lee Hooker, that seems to be George's biggest influence.
http://www.youtube.com/watch?v=BIvka3SSv9Y
There is a ton of killer blues music, but during the big blues boom in the 60/70s, i think much of it got too 'fancy'. A lot of the upbeat Chicago stuff i really don't like at all. I do however absolutely love Canned Heat as a more blues/blues rock type of thing. Howlin' Wolf, Muddy Waters, Son House, and tons more.
http://www.youtube.com/watch?v=tyfgb9sDT1I
Also be sure to check out early Peter Green era Fleetwood Mac for some great blues rock.
http://www.youtube.com/watch?v=HQ8AcEYTEFY
One of my favorite blues guitarists is definitely Albert King, probably Stevie Ray Vaughn's biggest influence (even though I don't like SRV). I had a Albert King live in San Francisco tape that I listened to in almost constant loop for 2 years. It rules so hard. When I dream, I dream of playing with a band/artists that play together like this.
http://www.youtube.com/watch?v=BIMcqzgDChw
I feel a lot of players are intensely overrated, such as Clapton. I just can not get into his stuff at all, I feel nothing from it.