The win sealed the Premier League title for United.
Asked if Van Persie's second strike was the goal of the season, Ferguson said: "It was goal of the century for me! It was a marvellous hit, head down, over the ball, perfect timing - a magnificent strike.
"He's been unbelievable, his early form in the first six months was fantastic. He had the spell where he didn't score but he was unbelievable tonight."