Some are mad that the Adventure Game is dead.
Some are mad that Sierra dishes out perpetual rehashes of Half-Life
(which is of course more a fault of Valve since they've clammed up).
Some are mad that Sierra/Dynamix botched Tribes 2
(especially if they suffered through the initial release at full price).
Some are mad that Sierra cancelled "game X" (Babylon 5
Really though ultimately people are mad that a beloved icon of their youth is now merely a software label entrenched in a corporate mess and that what was popular in their youth is gone (i.e., the Quest
series of games). Sometimes people want to rebel against something.