I really do not think this poll is taking the best...it is more towards favorite. I think there is a very distinct difference between the two.
One's favorite is a personal meaning, but the best is showing the band's greatest achievements. Now, sometimes they turn out to be the same, but not always.
I personally think Ghost Reveries is the band's best album, but it is not my favorite. Ghost Reveries shows where the band has been trying to get to all these years, there most solid effort, in my opinion. While I do not get as much from it as I do My Arms, Your Hearse or Still Life, I can totally see the band improving itself, getting the sounds they wanted, having each song be what it was supposed to be (even if I disagree with a few things, I know the band is happy with it).
So yeah, I voted Ghost Reveries for that reason.