I'm not really a huge fan of any of these 3.
Drake > Kendrick > Cole
Cole has a few standout cuts I like but otherwise his music is drab to me. The Game analogy of him being a fan and trying to replicate what he's liked from other already established artist rings true.
I'm not a fan of Kendrick vocally on most tracks. Musically GKMC bangs but if you don't feel an MC's voice you're not going to rank them highly. I do LOVE B Don't Kill My Vibe though, and respect his message. His voice is just naturally small. When he tries to get loud there's rasp instead of boom like a KRS/Chuck D/Pac. Not feelin it. For my taste he should stick to the mood music like Poetic Justice etc.
Drake has the most songs outta these 3 that I like, he's got a few different vocal styles that work for him and let him make a few different types of songs that I like. If Kendrick had his vocals he would destroy him though, cuz Drake makes cringeworthy lyrical/theme choices at times. Both of the other guys edge him out there, but I rank Drake ahead of them purely off vocal talent.
Big Krit > all of them