Wilson has joined Aberdeen on-loan from United.
Blackmore said, “Some players get their breaks at different ages.
“Look at Jamie Vardy, who took longer than most. Willo is better than Vardy for me.
“Maybe he's not quite as quick, but he runs better with the ball and he's two footed.
“James Wilson was the best 15-year-old I've ever seen. He was a fantastic finisher with his left foot as good as his right.
“His movement was very good and he steadily improved as he went through the age groups right up to making his first team debut, when he scored two goals under Ryan Giggs.
“James had a bad injury but he's still a top player. He just needs to be played in the right position."