The Clash: More Then They Seem?

I was looking through my iPod for something to listen to and settled on The Clash recently.  I figured "hey, I haven't listened to them in a little while".  I started listening and was thinking that they didn't sound all that much like what I know to be punk.  People refer to them in the same vein as The Sex Pistols and The Ramones because they were the forerunners of Punk Rock.  However, The Clash has a sound that is much more.