Three games come to mind.
The first two, MOO 3 and Elemental: War of Magic, are the first games that I remember following development in the gaming press and on forums and reading development diaries for. I preordered Elemental and bought MOO 3 on release day. Both were huge dissapointments and are responsible for my policy of never preordering or buying on release, especially for 4X or complex strategy games or RPGs.
The third is Undertale. I can see why so many people liked it, but it never clicked for me.