Atari 2600
E.T.
Pac-man
Donkey Kong

Commodore 64
Hunchback at the Olympics only good thing about this was the funny scenes you get when you fail a event

NES
Castlevania 2 Simon's quest
Captain Skyhawk
Predator

PC
Ultima IX hey it's my opinion, you don't have to agree but it doesn't change that I can't stand this game

Hmm, looking back it seems that there never was a NES version of the E.T. game. I'm almost tempted to go dig it out of its box in the basement and double-check it. I probably won't though, that thing scarred me for life.

I don't LOVE it, but I do think it's a decent game. The biggest problem for me is the silly way the item feeds work. Having better gear shouldn't prevent your character from having other better gear, and the fact that the feeds scale a lot faster than your abilities scale just makes it irritating later, especially when the decent item mods have 10+ Will requirements. I usually just hex-edit the feeds down to something more reasonable, which makes the game a LOT more enjoyable for me.

Spectral Force Genesis.

I was even expecting it to be bad (but at least not be a crappy port like the PSP games) but it turned out to be so much worse.

From the one's that I've completed so far...

Darkstar One has been the worst, I think.

Tomb Raider - Angel of Darkness. Piece of crap came free with my old video card and it still wasn't worth it.

Tekken 6. Insipid single player modes, frustrating, unfairly high difficulty even on easy and possibly the cheapest, most broken final boss I've ever seen. Gil, Seth and SNK bosses have nothing on Azazel.

But the worst I've owned (but since rid myself of) would have to be Bart vs The Space Mutants for NES.

I actually only mentioned the pickaxe thing along the way, I did not claim that it's one of the reasons why the game sucks - but it reflects upon the game's overall quality. Another thing that shows how moronic this game is, however, is the fact that pretty much every campaign scenario has its own set of special rules to keep the game at all challenging. "In this scenario you are not allowed to use unit XYZ", "in this scenario you can only get ressources by BLABLABLA" - then there's a scenario that seems almost too easy, but suddenly the game tells you "we cannot deliver any more tanks" out of nowhere which is the game's way of telling you "we suck at programming a strong AI or professionally designing challenges so we make this game harder this illogical way". Good gamedesign is about creating a solid set of rules and using it in different contexts or expanding upon it - that the developers had to customize the rules per scenario to keep the game the slightest bit interesting shows how flawed the core gameplay is. I was also shocked by the fact that in skirmish/multiplayer mode there aren't even real factions but that there's one generic army that can be slightly modified. I though it's a game about different civilizations! And yeah, even the inclusion and use of 3D is something that absolutely didn't impress me. There had already been a good portion of 3D RTS games at the time and EE just didn't impress me, especially since Warrior Kings was already around the corner (released four months after EE) and it made me laugh at the visuals and scale of EE.

Hmm...

It's a two-way tie between 'Bioshock' and 'GTA: San Andreas'.

Bioshock was obvious, clunky, and drama-free right up until I stopped playing it.
San Andreas... I just couldn't see the point of.

World in Conflict
i got it for 5 euros and remembered that it got pretty good scores when it came out. installed it, played a while and was bored to death. maybe it's not a bad game, but it just can't offer anything i would expect from a good rts.

Now that's a difficult questtion, because most of the games that I own I haven't played yet. So how am I supposed to know whether they suck or not?

The game which purchase I regretted the most probably was Diablo 2. But that doesn't mean it's a bad game, I just dont like how they turned a rogue-like into a grind fest. And I laid down a lot of money on day one for that game.

The worst game in my collection that I know of probably is Deus Ex 2. But that doesn't hurt as much because I got it for small money, already expecting it to be bad.

7th Guest. I also own 11th Hour, but as I haven't actually played it I can't mention it. Though I suspect I will hate it just as much.

The Phantom Menace. Okay, it's fun enough chopping up droids with a lightsaber, but really it's a pretty terrible game.

King's Quest: Mask of Eternity. It's alright storywise, but the controls are clunky as anything.
Nooooo! Okay, probably some nostalgia here, but I think it's probably my favourite of the Castlevania I've played (I should note I haven't really played anything since III, 2D platformers just aren't my thing anymore)

Tom Clancy's Splinter Cell - most railroaded game ever combined with behind-the-ass-camera, it lacked the very qualities that made Thief 1 and 2 such brilliant games: first person immersive gameplay where you rely on your hearing as well as your sight, and open ended levels to explore.

I also have Dragon Age and Mass Effect in my collection, but I haven't played them yet. If they are indeed "dating simulators" they will probably get second and third place.

Lots of answers in this thread.

Bottom line: it was made for consoles, so you were stuck with small, linear levels and inferior controls. Still, since I didn't except much from it when I found it in the bargain bin, I had some fun playing it.

Excpectations play a large role.

Ask the dev: http://www.youtube.com/watch?v=MGIdYl2oN74

Plus: It was the first poor port, that forced console limitations (ram, interface) on me as a pc gamer.

PS: You could also listen to the first five minutes of this video: http://www.youtube.com/watch?v=MGIdYl2oN74