Sachin isn't rated highly because Imran Khan set the tone early on by being on edge right from his debut. In the years that followed, he and Pakistan (because of his strong influence) became obsessed with finding a Pakistani answer to SRT. Truth is, Indian fans stopped being nervous when a Wasim Akram returned for a 2nd spell or in general, stopped feeling defeatist after the Miandad last ball six only because of Sachin. And you guys know this and resent him for that.
Kohli looks more Pakistani than Sachin. He has also been more openly friendly and careful with his behaviour around Pakistanis. So it became easier for him to be rated higher. It also coincided with a period in Pakistan where they were sliding down and so Kohli became aspirational. With Sachin, Pak were still dominant and it was a competitive issue too because Pak had become used to being dismissive of Indian players - they turned up at a game and simply believed they could boss the Indian team, but Sachin changed that.