Thanks Quintillus for the answer
It's a pity that the poll options are so limited.
In my opinion, they could be very interesting if well made.
I'll try to post a poll inside CivV subforum with 2 fake questions with multiple answers and see how it works.
EDIT: no, maybe it cannot work. The combinations would be too many (at least 58 only for the normal 5 games) and too difficult to read.
I'd like to see the results about the "Best Civ game" poll, but each choice should depend on how which games one has played!
Example results with fake votes:
I've played only to Civ 1,2 and the best is 2 ---------------10 votes
I've played only to Civ 2,3,4 and the best is 3 ---------------50 votes
I've played only to Civ 1,2,4,5 and the best is 5 -------------40 votes
I've played only to Civ 1,2,4,5 and the best is 1 -------------5 votes
I've played only to Civ 4,5 and the best is 5 -----------------70 votes
I've played only to Civ 2ac,4exp,5 and the best is 2ac -------5 votes
I've played only to Civ 3,4revo and the best is 3 -------------10 votes
..etc..