He's a physical monster, but in my opinion he hasn't shown a complete game that translates to the nba. He will be able to bully his way into the paint for a long time, but hasn't shown to have range or adeptness against a set defense/half court defense. He could be a less refined blake griffin coming out of college, or a more athletic julius Randle; which still a good player, and something you can build on.
But unless he becomes a defensive force, or playmaker, or shooter, to go along with physical monster, I don't see him a generational player. Regardless, a young blake griffin or athletic julius Randle is still someone you can take with the first pick.