If you look at that game cover and in your infinite wisdom still decide to purchase it, you deserve what you get. Sorry.
My younger self was a massive dickfuck for thinking that. Haven't put it in my system for at least 5 years. It's frightening. I see it glaring at me every night in my collection. It needs to be devoured by a bloodthirsty hydra sometime soon.
Not the worst game by any stretch but one game that I can remember being disappointed in was Mario 2.
It didn't play at all like a mario game and was just boring as hell. I remember as a kid being really fucking disappointed in it. Thankfully just about every Mario game that has come out since has been mostly awesome.
Pokemon Crystal... the Spanish knock off version. Was on holiday in Spain as a kid. Silver and Gold were the main ones out at the time, but they'd been out a while and I hear that a new one was coming out. And then I saw it in a shop in Spain. I bought it. Got it back to the apartment... and WTF IS THIS? A 2-D Mario style platformer with a Pikachu instead of Mario. Controls sucked. Difficulty was like Super Mario Bros 2 (aka The Lost Levels, the REAL one), except ten times worse. I don't think I ever made it past the first level. I just wish to fucking christ I kept hold of it lol. Certainly would be something for my collection .
New Update - May 24th 2016 - Big Cal Plays - Game Dev Tycoon - Episode 3!!!
The Beatiful Katamari comes to mind. How can a 360 game have such dated graphics, I saw better graphics on the PS1. It's also a glitchy, technical mess as well.
Other games that deserve mention:
Resident Evil 5
Resident Evil: Racoon City
Transformers: War for Cybertron
I think you are overreacting to "worst game". None of those with the exception of Postal 3 are even close to worst game ever. Same goes for whoever said Dragon Age Origins. DA: O is pretty good. It's even got a 91 on Metacritic. It may not be your type of game, but it's not worst game unless you've only played two games ever and Ocarina of Time is the only other game you played.
Bomberman Act Zero is the worse game I ever played. It was utter trash.