I agree they were fantastic but they never climbed to the heights in my eyes. Thief 2 and Deus Ex are one of the best games ever made and at this point if Dishonored doesn't amount to one of them I will be disappointed. I raised my standarts because I am tired of games with a whole lot of bark and absolutely no bite. So either Dishonored is great (it likely won't be) or I will be disappointed. I didn't feel that way until recently so my opinion could have been affected by a lot of things (I really don't care which to be honest). My point still stands, if it's not top quality, it's no quality.
We shall see when it comes out, but it sure looks like this game has more bite than bark. It seems like a very focused title. No convoluted "we make thrilling stories" promises with lots of cutscenes and fancy choices every minute. Just pure handcrafted levels with exploration and improvisation. Bioshock is't even close to this level of misson sandbox freedom, the released playthroughs and previews already show that much. At the same time this is clearly a much more handcrafted and atmospheric game than Assasins Creed etc. It may turn out to have som flaws but this has already proven itself to be the first game of it's kind since, well, Thief.
So time will tell if it will remain a classic. But this is, with no doubt at all, a game in the same spirit as Thief and DX1. Those games had flaws too, lots actually, but are still the best (and only) of their kind. Would you really miss out on another run down that line, even if the major reviewers don't like it 100%?