Well it depends on how you classify 'best' if you are going off trophies, what has he won? If football is not about winning things what is it about?
On the other hand if you are talking individual greatness then by every metric for a striker that exists Kane is world class, and stat wise up there with the very best to ever play, just played for a team well below his level for the majority of his career.
For the Rooney vs Kane debate it has to be Rooney, he is a CL winner on top of what? 5 times English champions trophy? Kane has won absolutely nothing of note. But if you are talking about who I would want leading my line as an out and out striker, Kane all day. Be interesting where he ends up in the all time debate once he hangs up his boots, still feel he has a few more years in him yet. Plenty of time to hoover up some trophies at Bayern.