I'd rather have a tighter, contained, and well paced short game over a bloated, filler-loaded long game.
I'd rather have a quality long game over a short game that doesn't go anywhere.
Etc.
Length is a factor, but not the deciding one.
The Order:1886 is mediocre because it has relatively generic combat, a standard story that feels like an opening chapter more so than a full narrative, and takes control away without giving anything in return.
Many sidequests in DA:I kill a quality experience with generic fetches, kill x missions, and slow flower picking. Running from resource node to resource node is not a compelling high fantasy experience.
[sub]inb4 "Get out of the hinterlands" - the entire game has this issue[/sub]
Portal is amazing because it has a consistent pace, a fantastic learning curve, and fun game play. It can be beaten in 90 minutes. It costs $10 on Steam, and launched as part of a $60 collection.
I like Deus Ex: Human Revolution over Far Cry 4 because the side content mattered more in HR, whereas FC4 had more content, but it was all filler. HR felt better paced, and as such felt like a stronger title, despite both having relatively similar gameplay.
I care if the game plays well. Then I care if there's compelling things to do in the game. Then I care if the story's any good. Then I care about length. Naturally, if any of those components are lacking, something has to pick up the slack. And if nothing does, then I hope the price points adjusts to match.