Rooney, a former Manchester United captain and the club's all-time record goalscorer, faces seeing his old team's two fiercest rivals fight for the title for the second campaign in a row.
Liverpool moved eight points clear at the top after Saturday's dramatic defeat of Leicester City, James Milner's 95th-minute penalty securing a 17th successive league win, with City in action at home to Wolves on Sunday.
"In my opinion, Liverpool look the strongest," D.C. United star Rooney told boxing outlet iFL TV after Gennady Golovkin beat Sergiy Derevyanchenko at Madison Square Garden.
"City are a fantastic team. I think Liverpool have improved on last year. City have stayed at that level of great consistency [but] I think Liverpool [will win the Premier League]."
Pressure is growing on Marco Silva with the Toffees 17th in the table, a point above the relegation zone, but Rooney expects his boyhood club to improve.
"I think the players are too good to be where they are in the league," he added of a side that signed Alex Iwobi, Moise Kean, Andre Gomes, Jean-Philippe Gbamin, Fabian Delph and Jonas Lossl in the summer transfer window.
"Once results start coming, they'll definitely get out of it."
A home clash against West Ham after the international break will give the Toffees a chance to get their season back on track before a tricky trip to Brighton – who recently beat Spurs 3-0 – at the AmEx Stadium to follow.