Giggs kept his run of scoring in every season since the Premier League began in 1992 against the Toffees to help United secure a 2-0 win at Old Trafford.
Ferguson told Sky Sports News: "He is an amazing human being, he is unbelievable. His energy and enthusiasm for the game is just incredible.
"I think all the superlatives have been used up and he doesn't need any because his legacy lives on.
"In this game again, at 38 years of age, or is he 39? Maybe 40, I don't know, but he's up and down that pitch all day and showing fantastic energy for the game."
The 39-year-old has now made 929 appearances for United in a career spanning 22 years.