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.
I don’t really understand the premise. The point of being patient imo is to avoid the hype.
So I’ll just answer the question if disappointment in games generally:
The Legend of Zelda: Breath of the Wild. It knew it was different, but it still didn’t feel like Zelda to me, so it didn’t scratch that itch I had. I’m enjoying Skyward Sword much more than BotW, the first dungeon just feels like I’m back in Ocarina of Time, the forest feels like Minish Cap somehow, and the premise reminds me of the original The Legend of Zelda (get the sword and go off on an adventure without knowing where you’re headed). BotW is my least favorite Zelda game, mostly because of disappointment. When I heard Tears of the Kingdom was much the same, I didn’t bother getting it. Maybe I’ll get it eventually, but I have no desire to play it.
Borderlands. I had avoided the game so successfully that I knew nothing about it other than that it was a shooter RPG, but I knew it was popular among friends. I missed the window when it came out, so I figured I’d give it a shot. After about 15 minutes, I realized it was just a looter shooter and noped right out. For some reason, I absolutely hate the genre and was disappointed that’s what my friends were so hyped for.
Lords of the Realm III. I loved Lords of the Realm 2 as a kid and played the original at a friend’s house and enjoyed that too. So when Lords of the Realm III came out, I naturally wanted it. However, they threw out pretty much everything I liked about the previous games (strategy around county/resource management) and doubled down on everything I didn’t like as much (sieges) and it just felt like a worse version of the Total War games. Because of this game, one of my life’s goals is to remake Lords of the Realm by preserving the good parts of each game in the series, essentially to make the Lords 3 game I wanted.
So these days, I watch gameplay footage before diving in to a game, because that would’ve avoided my problems with each of the above. There isn’t really a game I’m waiting for, I just have a big wishlist of games that looked interesting at one point that I’ll review when I’m looking for a new game to play.