I have to say that I'm a bit surprised at the poll results. I would assume that since this is a fan site, most people would find something redeemable about each album. So with DT having a small fan base to begin with, then 40% of them would throw out one or more of their albums, that doesn't leave very many people that share my opinion. Quite a shame actually. People just don't have the time for (good) music anymore.
It's more the way you phrased the question. You didn't ask if there were any albums with songs we don't like; you asked if there were any unlistenable albums, and that is open to many different interpretations.
I almost always listen to albums all the way through. If there's an album I really like except for one song, maybe two, there's always the Skip button. But if I find that I really can't stand that one song, to the point where I'd rather skip it than listen to it, then the album -- as a whole -- is unlistenable. That's my definition. I can't just put it on and play it through.
I've been a Dream Theater fan since Kevin Moore. Those early albums hold a special place and I can listen to
Images and Words and
Awake straight through. Same with
A Change of Seasons and -- yes -- even
Falling Into Infinity. But recent DT albums all have at least a track or two that just don't work for me, they're the ones I skip. So ultimately, if I'm in the mood for some DT, I put on one of the earlier albums. The result is that I
never listen to the later stuff. Are they truly "unlistenable"? Again, that depends on your definition. But I don't listen to them, so...