Are you forgetting Hakkinen?
Mika Hakkinen is the guy who gave those harrowing experiences for Schumacher. It was in Spa 2000, where Schumacher set the trend for forcing driver off the track, to which Mika responded with a stunning overtake in Spa 2001, leaving Schumi clueless.
Montoya is a very emotional character, who did his best in Willams keeping Ralf at bay. Back then in 2001,02 and 03, Williams had a stronger overall package with BMW power and it helped Montoya considerably. The BMW engine combined with williams aero, made them the king of straight line racing. In 2001 brazil and 2002 germany, he had sufficient straight line speed to lineup behind Schumi and pass him.
He simply didn't fit into Mclaren scheme of things. Though Mclaren was a much better car in second half of 2005, i never saw JPM push the car to the limit. He was always behind or tailing Kimi. He looked like he has lost the zest or zeal to compete. He could have performed much better if he was around for another year.