He told BBC Sport: “People think Barcelona are the best but they are not.
“Manchester City and Liverpool are more of a team than Barcelona - and Liverpool are more of a team than City.
“In my philosophy the best team shall win but I hope for City because they play the best football.”
Liverpool reached the final last year only to be beaten by Real Madrid after Mohamed Salah went off injured early.
Man Utd fans will not be happy with Louis van Gaal's Champions League prediction (Image: GETTY)
Liverpool boss Jurgen Klopp will want to go one better than last year's final defeat (Image: GETTY)
Van Gaal also revealed he could have chosen Tottenham over United when he was offered the manager’s job.
“Tottenham were a better selection because Manchester United were an old team and I knew I would have to transform them,” he explained.
“Was it the wrong choice? Maybe, but I follow my heart.
“I worked at the number one team in the Netherlands, Germany, Spain and now also in England.”
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Liverpool: Balague reveals why Mane won't go to Real Madrid
Man Utd face Barcelona and Lionel Messi in the quarter-finals (Image: GETTY)