Mass Effect Andromeda was painful to go through, knowing where it would end.

Other one that was hyped to no end was Driv3r.

For me personally, Death Stranding

Well then...good to know...I won't be wasting my money on that POS game.

Welp I didn't mean it's not worth giving a try, especially now it was likely to be on heavy discount, game is still good, even fantastic in some aspects, but I did have too much hype for this game for a long time since its reveal and I am a big Kojima fan, but it turned out to be just not as impressive as I expected it to be gameplay wise.

Daikatana John Romero made nobody his bitch with that one.
No Man's Sky Many promised features missing at launch, making it very disappointing
FF XIII, FF XV, FF VII R: Squeenix tries to reinvent FF every time again, especially it's combat system. It broke what was fine,and the story is all over the place now these days.
Any new EA game in those last 10 years (ever since Dragon Age: Origins Awakening), most notably Anthem, Mass Effect Andromeda and Star Wars: Battlefront.

the conduit. at the time i only had a wii and was craving a good fps. watched all the trailers and gameplay videos. was wowed by the graphics. bought into the hype completely. got it on launch day, beat it on launch day. was left feeling like i played a generic shooter. nothing worth coming back to or mentioning about the game.

I would bet that game had a pretty decent online mode...

As mentioned by op and others, FFXIII and FFXV were the worst disappointments following the biggest hypes.
I legitimately thought that FFXII E3 trailer was gameplay. So stupid. When it came I played the demo and new what it was. But the story is such a letdown aswell. And the charakters - yuck.
FFXV - naturally I was hyped for FF VERSUS XIII, but I thought XV carried on everything versus XIII would have been. And I played the demo for this one aswell (episode duscea) and I super mega hyper enjoyed it. Watched the anime - not bad at all. The only game I ever pre-ordered. The 90 € edition coming with the movie. I watched the movie online before the game released - what a dumpster fire. I could not face the facts. Kept my preorder and looked forward to it. It was boring and illogical in every single part that comprised the game - narrative, overall gameplay, combat, pacing, just everything.
I recently watched the beginning of a playthrough of FFIX (a game I very much liked when I played it 15 years ago). What a difference. How inconceivably different and better those older FFs were.
I wont allow myself to be hyped for FFXVI. Chances of that game being anywere as good as the PS1-offerings are very small.

The Last of Us, GTAIV.

Actually Rock Star games never live up to the hype. They’re all utterly dull. The Last of Us is definitely Naughty Dog’s weakest attempt. God of War 2018 couldn’t keep my interest, after an opening scene that actually was fun, either, but I didn’t have many expectations to begin with so there’s that. And then there’s of course the couple overhyped games that bombed but I personally never played.

Morrowind.  There used to be a time when I liked every RPG I played.  There was no distinction between Western and Japanese.  They were all good.  If they got advertised and reviewed well, then I was going to enjoy it.  The crappy ones were intentionally downplayed, so I could avoid them.  Then Morrowind came along.  What a piece of total trash.  This games takes everything I like about RPGs and gets rid of it.  Fun leveling?  Gone.  An engrossing story?  Gone.  A party to control?  Gone.  Explicit goals?  Gone.  This game is just not fun in any way.  I didn't know people could systematically destroy a whole genre like this.

Mario 64.  This game made me leave Nintendo for two generations.  It's not Mario.  It's an abomination posing as Mario.  Not only did it ruin the most popular franchise in gaming, but it was also made to showcase the worst controller ever made.  Years later I gave this game a second chance on the DS.  It still sucked.

The Wind Waker.  I saved the worst for last.  Or at least it's the most painful.  Objectively, Morrowind is probably a worse game, but Wind Waker destroyed my childhood in ways that George Lucas could only dream of.  When the Wii gets released, I go back and get a Gamecube to give Nintendo another chance.  Then I get to Wind Waker and I feel like crying.  This game combines the worst parts of Morrowind and Mario 64.  It systematically destroys my favorite Nintendo series, while being a total lie at the same time.  This is not Zelda.  The 3 NES/SNES Zelda games are the real Zelda.  Wind Waker is trash posing as Zelda.

I also have to mention Final Fantasys 13, just to emphasize how disappointing the top 3 games were.  Final Fantasy used to be my favorite series.  Now I don't even care about it anymore.  I played FF15 for one hour and then never touched it again.  I just didn't care to give it more of a chance than that.  My love for Final Fantasy gradually waned while playing the entire FF13 trilogy.  FF13 killed my love for my favorite series, and now I have no love for it at all.  And yet FF13 is not anywhere in the same league as Morrowind, Mario 64, and The Wind Waker.  There are plenty of parts of FF13 I really enjoy.  But the other 3 games are total trash and have no redeeming qualities whatsoever.

The worst part of all of this is actually the gaslighting.  I still hear people to this day trying to convince me that these are good games.  No, they aren't!  I've played them, and I know they suck!  Morrowind is probably the worst, because it's turned into Skyrim love.  I look at the reviews for Skyrim, "This game is great.  It's just like Morrowind."  Dammit!  So many people think Elder Scrolls are good games.  They have been gaslighted.  (At least this is how it feels to me.)  It sucks, because these games sell, and so more sucky games end up getting made.  Zelda actually got a course correction with Breath of the Wild, but Elder Scrolls and 3D Mario are still being made unchecked.  And these games end up influencing other games, so in the end there are fewer games out there which I actually like playing.  It sucks.