Think Cole has more in his locker as an emcee than the other two.
On an objective level, J Cole is able to engage listeners with his stories, and his production really complements that. I don't really get that yet from Kendrick. He's solid without being spectacular. I have yet to really sit down and listen to his new album though, so I'll definitely be checking that. Both of their production is also pretty solid without really pushing the envelope.
Drake is not an emcee I rate very highly, but objectively I think he's carved out a niche for himself in terms of his sound and his style of writing songs. There is some skill in being able to bring the mundane to life - but his production IMO is far better and more avant-garde than J Cole and Kendrick Lamar so that helps. Other than that, I find him very "meh" to listen to. But I understand why people like him.