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.
Dead Cells. I played for ~60 hours, but could not get the final boss down. It’s a tiny stage with a huge boss that has very quick combos that can 2 shot you. I tried a dozen times to figure him out in the training area (where you can practice boss fights) and I still couldn’t get it. It’s probably me though, my reflexes aren’t quite what they used to be.
Honestly my biggest problem with Dead Cells is that in Boss Cells 0 (BC for short) the game feels fun and fast but once you go to 2 and above it really feels like a slog to play for me.
Call it a skill issue but I have more fun on lower BC/difficulties than on the higher ones