Most people enjoy making lists of their "top 10" favourite games. But what about those games at the opposite end of the spectrum? What about those games that you thought were going to be complete genius, but when you actually sat down to play them, realized they were actually not living up to your high hopes?
Here's a list of my biggest disappointments. Thankfully, I don't have 10, or even 5 of them. ;)

Command and Conquer: As with most of my big disappointments, C&C was hyped and delayed for a long time. Magazines at the time gave glimpses of it, with tantalizing screenshots, over a period of what seemed like years. But I knew this game was going to be the big successor to Dune 2, which I had played to death and loved dearly.
Finally, C&C was released (with much higher system requirements than originally planned, of course, meaning I'd need a whole new computer to play it). The graphics were low-resolution and blurry. The gameplay was frustrating and idiotically difficult. The AI was moronic and irritating. And worst of all, the game had the EXACT SAME PROBLEMS that Dune 2 had! Maybe I would've enjoyed it more if I had tried the multiplayer, but I never had the opportinity.

X-Wing: As a huge Wing Commander fan, I felt like this game just couldn't miss. There was a gorgeous trailer for it released just before the game was finished, and I felt with a true 3D engine and the Star Wars license, it had to be briliant. Imagine my surprise when I first boot it up. The music is terrible and irritating and sounds nothing like Star Wars. The graphics are uniformly grey and bland. The mission objectives are confusing and frustrating (and even time-limited, making for an excruciating level of difficulty!). The game is unplayable with a mouse (unlike Wing Commander) so I have to invest in an expensive joystick. And of course, it's a bit buggy. Eventually I slogged my way through the whole thing, and I did sort of enjoy it, but I never felt like revisiting it afterwards...

Arx Fatalis: I had hoped this would be the beautiful modern remake of Ultima Underworld I had been craving for so long. The screenshots looked fantastic, and when a playable demo appeared, it seemed full of thrilling potential. I'm basically the first person in line to buy it when it hits shelves. And when I do, I play it obsessivly... for a little while. But something seems wrong. Some of that interactivity that was promised (literally on the back of the box) is nowhere to be found. The combat system feels a little bit broken. The NPC interaction is, well, non-existent. And the storyline is a mish-mash of all of the worst cliches in RPG history. I go on to finish it, eventually, but it all feels tedious, and as I try to let myself become immersed in it, something always yanks me back out of it. Despite the designers' lofty claims, it becomes clear that they really didn't understand what made Ultima Underworld so special.

Oblivion would be my biggest one... just not at all the great game Morrowind was. I guess Deus Ex Invisible War is another.
Funny thing is I enjoyed both of those games, despite what huge dissapointments they were.

Deus Ex Invisible War - Probably the game I was most excited for, and when I played it, I was very dissapointed. It's hard for me to play through the game and enjoy it, especially if I've played Deus Ex anytime recently. Universal ammo, the interface, the really strange sluggish movement, etc.
Resident Evil 4-5 - I am the one person in the world who doesn't like the way Resident Evil's direction took. Yes, the combat system is vastly superior to the old games, but the fact that the zombies, the monsters that made Resident Evil famous, were replaced with "infected" people who could still shoot at you, run after you, etc was a bit stupid. Even the infected people in 28 Days Later couldn't use weapons, and I loved that movie. I knew Resident Evil 5 was likely going to have similar issues, but I still played it and beat it. For me, I still want to see a Resident Evil game with Resident Evil 4-5 gameplay and graphics, but with the old school stuff of Resident Evil 1-CV. Unfortunately, I think this has basically been replaced by Dead Rising, which is awesome, but a bit silly.
Silent Hill Homecoming - The Silent Hill game so bad, the Japanese refuse to release it. Despite it not being produced by Team Silent, I had high hopes for it, since I had played Silent Hill Origins, and I felt that was a great game, capturing what made Silent Hill awesome. When I rented Homecoming, I beat it rather quickly, and the BIGGEST problem with it was it trying to introduce the Silent Hill movie as canon within the series. The game copies parts of the movie so accurately that it makes me wonder if there was a deal with the company that filmed it. I recently bought it since I'm playing through the whole Silent Hill series on my winter break, but I found it brand new at Fry's for $13 for PS3, so it's good in that sense :P

Star Control 3: After the masterpiece that was Starcon2, #3 was a huuuge let down.
MOO3: See above
and I'll throw Oblivion in there too, gameplay itself was improved, but the world was a let-down, pretty but hollow and repetitive. In Morrowind you could actually discover really awesome locations and creatures, Oblivion everything was the same and leveled with you, took out all the fun of exploration.

Star Trek: Legacy. Mad Doc and Bethesda promised state of the art graphics, competitive online gaming and a story written by the actual Next Generation writers taking in all 5 Captains. We got last gen graphics, a broken online game that was disgustingly imbalanced and a work experience guy who once stepped on the set of Voyager wrote a script that only Stewart and Shatner took seriously. Backula, Brooks and Mulgrew might as well have phoned in their parts.
Shadowrun. Microsoft promised big things from the console version of Counter Strike (their words) not to mention many gamers have fond memories of the classic Megadrive and SNES RPG's. We got a bland shooter with broken crossplatform play and FASA studios was closed thanks to Microsoft's stupid decision to make PC gamers have an Xbox Gold Live account to play online. Shdowrun was not bad as it goes just an absolute criminal waste of a huge name.
Saints Row 2. Specifically the PC version. Saints Row 2 is actually a very, very fun game until it crashes. It crashes a lot. So much so that Volition and THQ decided not to bother fixing it. The 360 and PS3 versions are still getting content added but the PC version has had all support officially pulled with no reason given. IMO the simple reason is the port was out-sourced and they made such a complete mess of it THQ decided it would cost more money for them to fix than it was worth. Still I should have expected this from THQ given the problems with Dawn of War: Soulstorm and they still have not changed with Red Faction Guerrilla still having the 5.1 Sound bug and the version is still V1.00. So many THQ games stay at V1.00 but Saints Row 2 is the worst example of them all.

Never had a crash in Saint's Row 2 but you are correct that the port is crap, mostly because of pop-in issues and poor performance on kick-ass hardware.

Ultima 9 - the death knell of Origin Systems and a really well-crafted RPG series.
Oblivion - like a supermodel with her brain removed: pretty but not much substance behind the flash.
Ultima 8 - AKA Super Avatar Brothers. It did have the annoying jumping bits patched out later but it still reeked of pure suck. AKA the first nail in the coffin of Origin Systems. Ultima 9 was the second.

Can I have a fourth? Valve have just announced that The Bards Tale is now on Steam. Terrible, awful absolute abomination to the name of the series. If anyone played the original Amiga or DOS versions then AVOID with a ten foot barge pole.

Spore : despite the marketing harassment, I wasn't expecting much but I got to play that game and even if it was entertaining to create your creatures, the game overall was quite disappointing. You go through different evolution phases (some are quite amusing indeed), but as soon as you have completed the couple objectives given to you, you skip to the next stage. It feels like playing a succession of tutorials without having time to really enjoy the game. Something is missing and the game seems incomplete. I spent more time customizing my creatures, buildings and vehicles than playing the game.
Zelda DS : phantom hourglass : total failure. Too easy, the main temple concept is way too boring, the dungeons are too small, you play the game with the stylus only, and besides fishing in the middle of the ocean, there is not much to do. Garbage.

Hellgate London: I played Diablo 2 for at least 2,000 hours and upon seeing this bought a new computer (my first computer that was mine btw) just for this game. Four years and a buggy release later it shits on the promises made.
Halo 2: Odd choice I know for sure but the original was one of the first games I played online extensively (PC version of course). Loved the mod support and good community (in the day... don't try playing it now) but the sequel had almost no mod support and was a half-assed port.

Deus Ex Invisible War - crushingly disappointing. Deus Ex was a game where the first map took up the whole of Liberty Island and left you to your own devices in how you approached it. IW was a cramped console port with crippling constant disc checking and where your first level was a single small floor of a building and every crappily designed level after that was equally cramped. That it was so dumbed down was less annoying than the fact that they had to fit it within the Xbox's limitations.
Oblivion - I was another Morrowind fan hoping that this would deliver something similar but I just found it bland. Nothing exactly wrong with it. Just not very interesting at all. Luckily Fallout 3 saw Bethesda make a return to form with a game that was actually very enjoyable.
STALKER Clear Sky - I was hoping that Clear Sky was going to be the game the excellent original was meant to be. Instead it was just more of the same buggy unfinished crap. Only this time with retarded TAGES install limits turning it into rentware. Worthless.

F.E.A.R 2 was a huge letdown. I bought it without hesitation before I saw any reviews thinking that same magic that permeated the original would be there. It wasn't. That game single handedly made me wary of ever purchasing a full price game again. The crazy part is technically it's not a bad game just nowhere near what I expected (and a lot of others thought the same too).

FEAR 2 scared the shit out of me alot of the time, and I actually found it more fun and less repetitive (in environments anyways) than the first game.
And they retconned the horrible expansions :P

Manjini/Ganados are more Lovecraft than Romero, which is a great improvement. They are zombie-like in that they are mindless and lust for blood, but these possessed villagers are intelligent and capable of cooperating, which replaces cheap scares with more substantive thrills. Also, putting RE5's Chris Redfield against RE's zombies would result in an undead massacre. RE's Chris had skinny arms and a worthless knife, but his older self is a murder machine. Those biceps are too much for the undead!