If we're talking overall influence, it's Dr. Dre and then everyone else can get far back in line.
Kanye likes to claim that his music wasn't about gangster rap and that's why he was sidelined for... a couple years... meanwhile, Dre not only made NWA and Snoop Dogg but managed to convince the entire rap world that a poor white kid with drug problems and abuse issues was the next huge thing by doing things that nobody had ever thought to do before.
Kanye’s 808 & Heartbreaks has been claimed by many rappers from the 2010’s and onwards to have been a major influence. He really went all in on autotune and introspective lyrics. I much prefer Dre but his influence is waning.
The specific claim was "the most popular rapper/hip hop artist of all time". For that claim, I don't see a good reason why the last decade should weigh more heavily than the decades before.
Kanye likes to claim that his music wasn't about gangster rap and that's why he was sidelined for... a couple years... meanwhile, Dre not only made NWA and Snoop Dogg but managed to convince the entire rap world that a poor white kid with drug problems and abuse issues was the next huge thing by doing things that nobody had ever thought to do before.