The lethal left-arm paceman captured three for 40 as England surrendered to a 281-run defeat in the final Test to finish with 37 wickets for the series at 13.97. (Agencies)
Johnson edged wicketkeeper Brad Haddin as the man of the series, and he set the tone for Australia's domination with man-of-the-match honours in three of the five Tests.
Clarke said 32-year-old Johnson's sustained aggressive bowling throughout the series was an amazing achievement.
"I hate to say I told you all so but I told you all so," Clarke chided reporters at his post-match conference.
"Man of the series, who would have thought? Except me and perhaps Mitch. He's been an amazing bowler for a long time. I think the way he's come back into this team... he's bowled with great aggression,” he said.
"To be able to do bowl at that pace is one thing, to do it for five Test matches, every single innings to be able to back it up is an amazing achievement,” he said.
Clarke said Johnson ranks alongside modern-day Australian pace greats with his Ashes performances.
"Mitchell bowled a couple of spells in this series that are without doubt as good a spells as I've seen in my career," the skipper said.
"And I've been lucky enough to play with Glenn McGrath, Jason Gillespie, Brett Lee and Shane Warne. Mitch's spells certainly match the greats, if not better. He deserves all the credit he's received, he's copped a lot of criticism, he's been dropped from the team,” he said.
"No one in the world can doubt Mitchell Johnson's character ever again,” he added.
"He's as tough a cricketer as I've played with, to be able to come back from the criticism he's copped, to be dropped at an older age and have the attitude and hunger to say 'No, I'm not going to give up', credit to him. He deserves the accolades."
The lethal left-arm paceman captured three for 40 as England surrendered to a 281-run defeat in the final Test to finish with 37 wickets for the series at 13.97.