He is MUCH MUCH better than Rubio (unfair comparison, because Rubio is a PG and Doncic can play multiple positions). As some of you have said, let's wait for his body to stop growing because he is listed 6'7" or already 6'8" depending on the source. Rubio had clear flaws in his game such as shooting or long possessions, Doncic is a player with no clear handicaps.
In Spain, we have a different categories. He's grown 3 centimetres since summer, and he is listed as 2'01 metres now (6'7" is the closest in feet-inches). The most popular comparison here is Anfernee Hardaway.