Guys, don't just list bad games. Sonic 6 was a very complete game, it has a decent number of levels, you could play through it four times for four different endings, everything about it was complete. Maybe buggy and crappy, but complete.
Now compare that to Xenogears. Much of the third disc was a person in a rocking chair telling the story, because they were forced to wrap the game up before it was complete - they had to cut a number of dungeons and stuff and replace them with the rocking chair.
Another example, Ultima IX - pretty much the same situation, EA surprised them with a sudden decision that the game needed to be done quite a bit earlier than originally planned, so they had to change much of the story to fit the content they had completed. If you watch the videos on the disc, they tell a different story than was in the game, though you can see they used whatever chunks of those videos they could to craft a new, shorter story.
I would say that Zelda: Wind Waker fits in this as well, though not as blatantly - the game only has three real dungeons, the least of all Zelda games, and one of the people in charge (I think Aunoma, I forget) said they wanted to make three more dungeons but the game was rushed out.