One can not zone into a SINGLE game for the worst ending ever.
See, from a creators point of view, they can hide behind the weak excuse that they're "setting up the franchise for expansion", or "story wasn't the key element you should have focused on", etc.
Personally, I've seen a lot of bad endings. Borderlands is popular amongst people here, I can see why. It offers no form of closure, was extremely anticlimactic, and just summed up my opinions on the game as a whole: bad.
Im not a fan of Assassins Creed's style of ending a game. I get it, franchise. But deliberately making 100% of your userbase go "WTFrench toast was that shit!" after every game is NOT doing it right.
Golden Sun on the GBA. Great game. But the first ones ending made me want to punch a hole in a wall. Seriously, epic cliff-hanger.
Fallout 3's ending was... alright. But I'm including it because I didnt like the progression ark. Get us intersted in the story, BAM ITS OVER LIKE THAT. NOPE, SORRY. Ugh.
Generally, I tend to be conservative about buying games. I will hardly ever drop the cash on the first day for a game, save for a few series that actually interest me (Im one of THOSE people whose generally intersted in Halo. Except ODST. That can just go die, horribly.) While I tend to buy games that have bad stories, they are usually games I dont buy for the single player experience: they're games I buy for the multiplayer experience. Plenty of games have bad endings, thats pretty much a staple in the industry right now.
As for Fable 2 having the worst ending, it's kind of fitting. Thats the only game I've ever played only a little bit through before returning it to the store. I was not interested in spending my time to get to the end. Worst ending ever, or does it fit into context with that game being so deliciously... bad...