I try to keep my expectations really really really low so I don't get all pissed off when a game does suck, I'd just return it if it's not good. although, I didn't have much problem with that vampire game besides the linear part, the game looked fine for it's time and the control isn't too bad, the memory leak was horrible though, the only recent game I can think of that had a memory leak that bad was Prince of Persia(new one) on the PC.

My biggest gaming dissapointments.  They are many, and have made me more aware to my gaming purchases:

Rogue Squadron: Rebel Strike - (Following the success of the second Rogue Squadron game, released at the launch of the GameCube with only 7 months of development, Factor 5 decided to make another for the GameCube.  Yet somehow, even with over 2 years of time to work on the game...they botched it up miserably.  Adding gimmicky ground based battles with horrible controls, the game was an embarrassment to play.)

Pokemon Battle Revolution - (What looked to be a step up for console based Pokemon games was even more of a step down.)

Dragon Quest IV DS - (The game has such a bad localization and next to no marketing that what was suppose to be the revival of Dragon Quest in America turned into the second death of the series.)

Castlevania: Lament of Innocence - (I expected IGA and Konami to follow the lead of most other companies and take the time a major 2D franchise needs to tranfter into 3D.  Instead, all I got was a bunch of cool looking previews...and a game that was not as good as my expectations or the previews.)

Soul Calibur II - (Soul Calibur was the reason I got a Dreamcast.  So when Soul Calibur II was coming out, I was pumped.  But then when it came...nearly everything I liekd about the original was changed.  Hwang was removed and repeaced with a character who plays like a fusion of Sueng Mina and him.  The game was sped up.  Various characters moves were changed.  Ring Outs were much easier.  etc.  In all, it was not to my liking at all and took the series in a direction I couldn't enjoy.)

Suikoden IV/V - (Being a huge fan of Suikoden, I was egarly awaiting more Suikoden games.  But after the creator left, it was unclear where the series would go.  Well, when these games came out, the answer became clear.  They no longer followed the main storyline of the previous games and become 'stand alone' stories only following the formula of Suikoden with character cameos and references to the past overall plot.  For this, they are one of my biggest gaming dissapointments as they ruined one of my favorite gaming series by effectively killing the entire point of Suikoden.  Having an ever evolving and connected storyline.)

Halo 3 was a dissappointment.

Soul Caliber 4 aswell.

this

GameCube in general was a console I bought with great expectations and in the end become one of my biggest regrets of my gaming life.

I once used to be very excited for MGS4 and RE5, but gradually the excitement receded and devolved into loathing instead.

I'd say WarioWare, MadWorld, N3, Brawl, Castlevania: Dracula X Chronicles, Lair, Calling All Cars, and a few more.

PES08 & PES09 for the Wii
& Twisted Metal Black

Mirror's Edge. It looked so hot from the E3 trailers, but the really sucky story and the dumb combat pulled it down...