The problem with such a poll is that is completely generation baised. Cule or not, if you grew up watching Ronaldo, he is the reason you watched football. People 7 or so years younger than us will hail Messi.
Until this day I long for the same feeling I used to get when watching Ronaldo. It is purely subjective because of the fact that he planted all that I love about football. But I was a child whose love for the game was unpolluted by politics, tactics, results, history and so on. Purely football technique. Growing up on Ronaldo will always sway my decision.
I have read a few things on here about Messi being a more complete player and so forth but the rest of the discussion was incomplete and it is apparent that they lack knowledge about Ronaldo between 19-23. Ronaldo danced the ball away from two to three players, where as Messi moved/swerved away from players towards the goal. When Messi plays, he shocks his opponents with his speed and ball control whereas Ronaldo entertained the crowd first. There is very little flashyness to Messi whereas there was a lack of directness to Ronaldo.
Both from different schools of thought, from different eras and it is unfair to compare them. My pick is subjective and I admit that, for that Il Fenomeno is the king of the pitch as far as I am concerned.