I kind of liked MM8, but I will be the first to admit that it was very flawed.

The actual adventuring was fine, it just didn't really add anything over MM7. MM7 had a similar cop-out at the end but it was actually cool, in a way like the ending to William Gibson's sprawl trilogy. MM8's ending cinematic didn't seem to agree with the dialogue.

I still in a way like Ultima 9, for the spellbook and first few shrines and dungeons, it did partly succeed. But it did fall really short of what we needed in a goodbye and even with unofficial patches the second half is a trainwreck. I was alright with U8, it just wasn't an Ultima game and could've tried a bit harder.

Off the top of my head I can't think of the most disappointing one ever. But of recent games I've played (and possibly ever), it is definitely Turok 2. I played Evolution when I was a kid, and I had fun with it but from what I remember I wouldn't necessarily call it a great game. That was the only Turok game I had played up until I got Turok: Dinosaur Hunter from GOG. I had a fantastic time playing that, even though it was a little short. After being a little surprised at just how much fun I had with that, I was fairly eager to try Turok 2 when it came out on here.

Despite keeping my expectations down for the most part (although admittedly seeing the reviews made me more hopeful), I was incredibly disappointed with Turok 2. And honestly, I kind of hate the game. There were some fun parts, sure. But it was also a very up and down experience. In comparison to Turok 1, the pace felt pretty slow and the combat just wasn't as fun or visceral. The soundtrack was also pretty repetitive. And a first-person shooter story doesn't have to be mind-blowing, but goodness I could barely bring myself to care about it in Turok 2. If you're going to shift to a bit more story-oriented sequel, at least make it somewhat compelling.

But the worst thing, IMO, is how tedious it is to go through some of the levels, especially when you have to backtrack to get items you either missed or weren't able to get at the time. The level design could often be confusing, and the atrocious map didn't help either. Every single time I had to backtrack or go through the levels again in Turok 1, it was either "Oh, duh!" or "Crap, I forgot I wanted to go there." or "Looks like I should've gone that way first instead of the way I went." It was just a slog in Turok 2. Not even difficult, just tedious.

If Turok 3 makes it to GOG, I still want to try it though. But after Turok 2, I'll certainly be tempering my expectations.

Quite possibly Killzone: Shadowfall which I just wrote about in the Games Finished in 2017 thread. It's just worse than its predecessors in practically any regard, even the visuals. The music may be the only exception.

Ultima 2 probably also deserves a high spot. My expectations weren't too high since I was aware that it was a very early CRPG but I was expecting a major improvement over the original game while it ended up being worse in pretty much every regard.

Also a huge disappointment to me personally was Dawn of War 2 with its crappy singleplayer campaign and downscaled multiplayer mode with an increased focus on micromanagement (while the comparably small amount of necessary micromanagement was one of the main reasons why I preferred the original over Blizzard's RTS games).

Ah, and of course Vietcong 2, probably my biggest disappointment in a sequel ever. It just ruined literally everything that made the original game great. I'm still not sure how they managed to achieve that.

Yeah the gameworld and exploration was great. What kind of broke the game was that you could recruit NPCs as party members though. Being able to get a level 50 character very early really broke the game + the dragon characters.

The whole thing ended up being some easy playthrough.

Yeah the end cinematic in 8 did NOT fit the dialogue. You are right about that.

I still say 6 is the best one. Sadistic dungeons in the final third aside, the game was a rock solid game.

Kind of ironic though. The title. Might and Magic. You spend the whole game trying to master might and\or magic, but in the final bits of the game you have to master technology to beat the final enemies.

Skyward Sword and Twilight Princess are up there, for differing reasons.

I loved the engine too much not to enjoy Might and Magic VIII when it came out, but it's the only game from the latter trilogy I haven't replayed at some point. Just too easy. Last I checked no hard mod existed for it. :/

Mass Effect 2 - I like the first ME but the second one is just annoying.

Blackwell Epiphany - The ending is just at odds with whole established lore. And I was really disappointed after Blackwell Deception (previous game in the series) promised the whole different story, which was completely abandoned in Epiphany.

Most of the sequels,they nearly always make changes for the worse and sometimes it makes me think if they are idiots or never saw/played the original.

Try to beat it with your main character only, it will be much harder this way :)

I'm at the opposite end of that. The first game was fun, but Borderlands 2 addressed all the things I complained about in the first game. There was more story and character stuff to bind the whole thing together, for example.

Perhaps the experience of playing first Borderlands game was so unique to you that the sequel felt less exciting.

Every Final Fantasy after IX.

Oh man, there are many franchises like that (Europa Universalis, Settlers, Civilization, ... ).
Not that they are all mainstream, but most of them certainly sell enough to qualify as a mainstream game.
I mean, Hearts of Iron IV has sold over 500k units on Steam.

Deus Ex Invisible War and Elder Scrolls IV Oblivion strike out as the obvious runners up to me, but I'm gonna go with Dragon Age 2. I was a big lover of Dragon Age, it combined a lot of what I loved about old school isometric games and newer 3D games into one very PC focused package. The sequel tossed lots of that out and was super rushed, and then Awakening took a further crap on it. Awakening was the last big "blockbuster" game I played and I think it really soured me in general.