When TNG first came on, people were trying to draw parallels between the casts. The TOS triumvirate was Spock=Logic, McCoy=Emotion, Kirk=Balance.
In TNG, Data was obviously Spock, Picard was Kirk, and the obvious "emotion" analogue was Troi. That kinda left Riker out of the loop, and he was the First Officer, so some people tried to argue that he was really the McCoy (the "real McCoy" -- ha, I just thought of that) but that's just plain reaching. He did have a more impulsive side to him, though, emulating a lot of Kirk's "cowboy" diplomacy, etc. But for pure animal impulse and emotion, there's Worf. So complicated. I think the conclusion, such as it was, was that an obvious parallel didn't exist.