I think Beck is the best technical guitarist of the three, but Page is the best musician. His compositions are by far the best (as far as I go, the best in rock music), and as a producer, he knew better than the other two how his guitar sounds fit into the songs created by the band as a whole. Also, neither of the other two managed to sustain a band, let alone one composed of three other such superb musicians.
Jimmy Page was one of the top session players in Britain during the 60s (as was JPJ), so by the time Zep started he was already of master of the studio.