Very interesting poll but purposeless at the same time. It's almost as if to ask what is the best religion, the best god, the best anime in history.
I assume that some specification should have been made at least. The Best in last ten years, the best during this season or having the best form & fitness right now. Again there are very skillful scorers (who can dribble 3-4 players) or just the ones who has the perfect timing to be at the right place at the right time. The first are mainly contributors & the others are finishers.
F.e. we say that Messi is the best in something. But only when playing at Barca. Who knows what would happen had he played in Mallorca for instance. Present-time skills, fitness, manager, team strategy, team's potential, partners, position in the pitch are the main components of success.
So it seems that the perfect scorer is the temporary-bound term which applies to the person we had chance to observe for quite a long-lasting period of time.