to me the most legendary rivalries were those of riders from the same country: Bartali vs Coppi, Koblet vs Kübler, Anquetil vs Poulidor as in comparison e.g. Hinault vs Zoetemelk, Indurain vs Rominger or He-Who-Must-Not-Be-Named from Texas vs Ullrich ... in either group the rivalry was similar in terms of pure results, however very different in terms of emotions ... Boonen vs Cancellara was certainly a huge rivalry in terms of results, however definitely not one in terms of emotions (I can't recall the cycling-fan-world being devided in Pro-Boonen vs Pro-Cancellara) ....