I disagree ...
Fellaini and Kompany are the best performing Belgians
but Marouane isn't the most complete player, at least not in my eyes ... I have to say Witsel is the most complete player.
I really like him and I rate him a lot higher than Fellaini and Kompany!
The guy's got everything, pace(although you wouldn't say that when you see him run), aerial ability, technique, stamina, he can get forward, he can score and defensively he's not that bad either.
And he's only 19 ...
If you want my advise on who's the biggest Belgian prospect ... than I'd go for Witsel, followed by Hazard and Dembele.