smrtgi19: system shock
half life
It's the 3rd game curse.
Look at some of the 3rd games that weren't as good as the other two...
Mass Effect 3 (I disagree, I loved ME3, but quite a few folks hated it)
Dragon Age Inquisition (again, I actually thoroughly am enjoying it)
Van Helsing 3 (haven't played it yet, but it's scored significantly lower)
Risen 3 (same story as VH3)
Eschalon 3
The list goes on. I often wonder if it has to do with expectations. I think people put the 3rd game of a series on such a high pedestal (especially b/c the 3rd game is usually the last).
Some 3rd games are awesome though.
Morrowind (I think that was the 3rd main release?)
Fallout 3
Mass Effect 3 (my personal addition, though I think most folks put it in the above list)
The Witcher 3 (this one stands out as a great 3rd game).
Anyway, just my 2 cents.
gamefood: Counter question: why all has to be a trilogy these days?
The answer is Star Wars :-D