Scotland goalkeeper Craig Gordon denied the tireless Frank Ribery and Nicolas Anelka with two wonderful second-half saves. Scotland threw an iron curtain around Gordon's goal as Alex McLeish's side were content to concede possession and repel countless French attacks.
McFadden said on Sky Sports 1: "To win at Hampden was a bit of an upset. To come to France and beat them in a qualifier is unbelievable."
Asked if it was Scotland's finest result, he added: "I can't remember. They're up there with the best teams in the world and we've more than held our own and we've got a a win.
"It wasn't pretty at times, we defended well, we were solid and got a goal and won the game."
Of his decision to go for goal in the 64th minute, the Everton midfielder said: "We trained here last night and the balls were flying everywhere so I thought 'why not?"'
McFadden believes Scotland are now on course for a place in Euro 2008.
He added: "We've got a great chance now.
"We've got to believe we can win the rest of the games - why not?"