Depending on who you talk to, you'll get 2 or even 3 different comparisons. Style wise, I think his closest comparison is Gretzky. He's definitely an above average skater in regards to his straight line speed. His shiftiness and edge work though are elite and as good as they come. He is extremely elusive and greasy and has an ability to make people miss when trying to hit him. This kid can dangle and deke a defenceman basically at top speed and more often than not he maintains control of the puck. His creativeness, IQ, vision and playmaking skills are as good as you could ask for in a player/prospect, honestly watch him and you'll get what I mean. He has terrific hands, and he has the ability to make passes no one else on the ice can make. This is where I relate him to #99, he's also a killer behind the net. He has a very accurate shot and more importantly he understands when to pull the trigger. Despite comments from previous posters, he's actually very smart in his own end and has a knack for taking pucks off of guys, when he doesn't have the puck, he's always in pursuit of it.
Now it sounds like I just made him out to be the next Gretzky or Crosby, but that is not the case. While I think size literally has no bearing on a players ability to put up points, because smaller players are actually harder to catch and hit, therefore they generally tend to be more elusive to bigger and slower players. However, Gaudreau's biggest obstacle will be going to the net in the NHL. Teams in the NHL are coached so well and many defences will just collapse on their opposition and put up a wall in front of the net, therefore Gaudreau may be forced to play more of a perimeter game and take the role as more of a point guard. However, he is so darn smart and opportunistic, so he will eventually find the kinks in a teams armour and break through from time to time.
Gaudreau I think will bottom out as a 50-60pt top 6 winger, think Jiri Hudler. But I could see him producing similar to Kane and becoming a PPG player within a few seasons if he hits his ceiling. I do not think he will be the next Gretzky or Crosby, but I absolutely believe he is capable of being a very dynamic and productive player. Either way he is a human highlight reel and will be fun for all fans to watch.