I didn't mention Aguero because he's the only player who's consistently been among the best in the world during his time. The other two won't certainly be looked by history as far better than the ones I mentioned. I doubt, among the natural subjectivity of these things, that there is that much between them. Both Valdano and Burruchaga were "player of the year" in their respective leagues in 1986 (Spanish and French), something I doubt Di María or Higuaín will ever accomplish.Di Maria and Aguero, whom you have funnily failed to mention, are better than the three you mentioned.
I'm not even sure if Di Maria was ever player of the year in Portugal, during his long tenure here.