The returning Chelsea boss says the winning sides of the past two seasons - Manchester United and Manchester City - pale in comparison to title-winners of the past, including his own Chelsea side of 2004-06 vintage.
United won last season's title at a canter and although he believes the competition is collectively stronger, Mourinho does not think individual teams are as good as in the past.
Pointing also to Arsenal's 'Invincibles' and Carlo Ancelotti's Blues, as well as the Manchester United team of a few years ago, Mourinho said: "The champions, in other seasons, were magnificent. Especially in the last two seasons, I felt not.
"Sometimes you win because you are tremendous and other times you win because you are the best. But you can be the best without being tremendous.
"Do you think Man United last year won the Premier League because they were an unbelievable team? I don't think so.
"The other contenders, they didn't have a very good season.
"The same thing the season before, when Man City won the title in the last second of the competition.
"Were they an extraordinary team? I don't think they were."
Chelsea open their campaign at home to newly-promoted Hull on Sunday.
Meanwhile, Mourinho has little sympathy for David Moyes' frustration at United's start to the new season.
Moyes described an opening five-match sequence which includes games against Mourinho's Chelsea, Liverpool and Manchester City - as well as a tricky opening trip to Swansea - as the toughest the club have faced for 20 years and has sought reassurances from the Premier League the run of games was nothing more than coincidence.
It was the sort of conspiracy theory Moyes' predecessor Sir Alex Ferguson often aired during his near 27-year reign at Old Trafford.
Mourinho suggested that if he had shared the same views as Moyes, he would face disciplinary action.
"If I say that I'm in big trouble,'' he said.
"If I say that I put myself in a difficult situation, so do the same with David.''
He addressed the possibility of a conspiracy in jocular fashion, referring to "hot balls and cold balls'' and a computer virus.
"I was informed the fixtures were by computer, or old fashioned with hot balls and cold balls,'' Mourinho said.
"If it's a computer, unless the computer has a virus, I don't know.''