Well, they didn't have to call it "Amnesia: A Machine For Pigs" but simply "A Machine For Pigs" if they didn't want people to have certain expectations.

I'm not one to claim a sequel has to stick slavishly to the original formula, but where it deviates, it should do things better - otherwise the developers will have to take the criticism. Rating a game lowly solely because it is different from another game, of course, is weak, but if it so happens you actually dislike what is different or like it less than how it was in the original, it's totally okay to say so.

I haven't finished the game yet and so far, I feel like it does a few things worse than TDD and a few things better. Most important, it's scary again, so I'm content by now.

I didn't actually have a problem with Dear Esther -- but then again I got it in a Humble Bundle for pretty cheap, and I went into it having read all the myriad reviews that had come out about it by that point. It was interesting, but it certainly isn't something I'd be willing to pay a whole lot for. I played it once, found it interesting and unusual, figured I got my money's worth and that was it.

Having said that, AAMPF does have some similarities to DE -- there's a lot of the same notes being hit -- and it's worse off for having those similarities. It's not a bad game, and does have its redeeming qualities, but IMO it definitely fails to live up to The Dark Descent, and largely for reasons that relate back to the game development philosophies of the studio that made it. It was also not worth the amount of money I paid for it (considerably more than what I paid for Dear Esther).

At least I now know that I ought to be very wary about buying anything developed by The Chinese Room...

I just picked this up from the Halloween special. I decided after all the criticism leveled at it that I would simply treat it as its own thing, and I have to say I'm actually quite enjoying it. Great atmosphere. I also found myself thinking one could create a nice "Thief" game with this engine.

For me AMFP's most serious error was carrying the "Amnesia" title.

^ This.

If the game had cut all correlation with the previous titles, there's a significant chance most of the criticism wouldn't have existed. However, there's still the understandable alienation people felt from playing a "not-game" game. That's still an issue for most people, but is moreso a problem with expectations from the medium, which are now changing.