In my opinion, this question in its present form is entirely unanswerable. There are literally thousands of sets of criteria by which you could judge "greatest," and almost every one of them would lead you to a different answer. This question as it has been posed is much better suited to a "My Space" poll than it is to a site such as this, which aspires to set a higher standard for internet discourse. Perhaps you should rephrase the question into several different questions. For example:
1. What are the 10 most popular r&r bands of all time?
2. What are the 10 most musically skilled r&r bands of all time?
3. What 10 r&r bands have had the most social impact?
4. What are the 10 most commercially viable r&r bands of all time?
My point is that these specific questions could go on forever just based on the one vague question that was posed. No offense intended to the original questioner, but if the members of this site (myself included) are truly looking for a more thoughtful and intelligent dialouge than you get in an average "internet discussion group," the questions and/or "ideas" need to also be held to a higher standard.