A run doesn't mean you're necessarily the #1 rapper out. It means you're on a hot streak. That being said, you can't say that Drake's run didn't start in 2009:
2009- "Best I Ever Had", "Successful", the features on "Say Something", "Money To Blow", "Every Girl", "Bed Rock", a mixtape that was free that was sold at retail that went Gold
2010- several songs from Thank Me Later were in rotation ("Miss Me", "Over", "Find Your Love", "Fancy", and non-singles like the song with Jay and the one with Jeezy), he was featured on "Moment For Life" and there was Ross's "Aston Martin Music")
2011- Take Care which had "Headlines", "Motto", "Marvin's Room", "Take Care", "Make Me Proud". There's also the Khaled record "I'm On One". Then you have Wayne's "She Will".
2012- Ross's "Stay Scheming" and everybody was on that "you wasn't shooting with me in the gym" line (nowhere near best line of 2012, but it was the one that everyone seemed to love quoting). The singles from Take Care were still in rotation.
2013- Nothing Was The Same dropped and "Started From The Bottom" was possibly the biggest rap record of that year.
2014- That year is a blur. I don't remember much of anything from Drake in 2014. I don't remember much of anyone making noise in 2014 really.
2015- "Hotline Bling", "Back To Back", the beef, What A Time To Be Alive, If You're Reading This It's Too Late