Kane – linked with Real Madrid – has established himself as one of the most lethal strikers in Europe, having won back-to-back Premier League Golden Boot awards.
The 24-year-old tops the scoring charts again this season with 22 after reaching 100 Premier League goals in Tottenham's thrilling 2-2 draw at Liverpool Sunday.
Tottenham, fifth in the table and a point outside of the Champions League places, finished second last season, but Rooney warned Kane's motivation may turn from goals to trophies.
"At the moment, he is probably the best striker in Europe," Everton veteran Rooney told Sky Sports.
"He can go where he wants to, he's that good. He is like a young Alan Shearer. He scores all different types of goals.
"The problem that Tottenham are going to have is that his motivation is goals, but his motivation is going to change from goals to trophies.
"And if Tottenham don't win trophies in the next year, maybe two, he is going to want to move elsewhere to win trophies.
"That is a decision he is going to have to make in the next year or two, but Tottenham have also got to make a decision — bring more players in and have a real push to win the Premier League."
Rooney added: "The goals are great, and they take you to a certain level. But the top players are remembered for the trophies they have won. The trophies take you on to that next level.
"I think if Harry Kane was in Man City's team and was going to win the Premier League this season, people would be talking about Cristiano Ronaldo, Lionel Messi and Harry Kane."