Personally there are a few games which left me very dissappointed, after hyping myself up for years in certain cases.
Divinity Original Sin: turns out I prefer more streamlined, less packed games (love Pillars of Eternity) and that coop play in a CRPG stresses me out.
Wasteland 2: I actually managed to finish this one but secretly I admit I was hoping for a better Fallout which I didn’t really get. New Vegas did the cowboy theme much better.
INSIDE: while the design was cool, it was just a ton of boring, easy puzzles in comparison to LIMBO, its predecessor.
Assassin’s Creed III. I know it’s considered one of the weakest entries in the series, but I absolutely love the time period it’s set in. That alone had me excited. Decided to finally give it a try recently and quickly found out that all the criticisms are valid. It’s not very fun, the story is extremely bland, there are multiple glitches throughout, and the modern day sections are just the absolute worst. I don’t ever expect much when it comes to the AC series (especially the titles from that time) and can usually find something enjoyable in them. Not the case with III.