I'm not saying what I've voted for but am expecting Whole Lotta Love by Led Zep to be top, provided the 'kids' of today have actually heard of Jimmy Page et al!!
Actually, it wasn`t Street Fighting Man that I remember (although that was good). It was Gimme Shelter - surely one of the most memorable riffs of all time.
I too questioned why so many (what I consider to be) classics were missing.
Young Chill plays the sax and has recently turned to the guitar.
He tells me that a riff is different to a chord progression, hence some are not deemed riffs but chords.
That was his explanation, though I'm somewhat sceptical!
I had questions of my own i.e. why wasn't Message In A Bottle in there or Alternative Ulster by SLF? There were far better tracks too by the Manics, not to mention Dakota by the Phonics.