Did that question from a fan on American Idol the other night make you think about starting a thread like that here?
Anyhow, when you talk about rock'n roll I know most will refer to Chuck Berry being godfather of it, but for me the most influential rock music came from the "British Invasion" and others from back in the day. The Beatles, The Rolling Stones, The Who, The Kinks, The Yardbirds, The Animals, The Hollies, etc. And that was only the first wave. Then you get the second wave of bands like The Clash, The Police and the Sex Pistols who could of been considered just as influential but catering to a much different and younger crowd.
Brits hands down.