Aren't all polls self-selecting, given that most people who get a random survey thrust at them out of the blue will ignore it? People still choose whether they participate. This is just a discussion, the nay-sayers seem to be treating it with more importance than anyone else.
Let's assume BW did a random poll and put up the top 5 - odds are it would get shouted down with "let me guess... they asked 100 EA bean-counters and the Cartel Market won" style posts.
It wouldn't be "fair" unless Bioware sent out an email to every active account...
and even then the results would be "biased" because it's asking people who play the game what they
want, and not people who don't play the game what they would need in order to play the game, conveniently forgetting that people won't necessarily jump into subscriptions just because a game has PvP, or end-game, or Pokemon functionality, or poker, etc.