Well I just cant remember Barkovs another winger, but Ville Nieminen seasons in FEL:
09 - 10, 29 points
12 - 13, 50 points (career high) with Barkov
13 - 14, 22 points
Good grinder for sure but not really known offensive dynamo.
(Assume, Chris Connolly was another winger 0,72 ppg versus Barkovs 0,92)
For example Ilari Filppula over ppg last 3 seasons in fel. Dont really know with whom Kakko plays most.
Edit: I dont try to press down Kakko. For sure I would want him in Florida. But I just dont think he is easily better prospect than guy who had higher ppg, better defensive game and made his team mates better and already is arguably atleast top 15 center in NHL at the moment and havent reached his full potential yet.