Publishers often push developers into creating games that aren't fun, merely because the marketing folks at the publisher think that it'll sell. The publishers pay the bills, so the developers don't really get to say "no" -- especially if they are small or relative unknowns.
Bad games usually happen for two reasons:
(A) (less of the time) Some decision that some proud boss-type individual makes, makes the game bad. As an example, the former head of Atari, Bruno Bonnell, was famous for forcing boneheaded project-specific decisions, and then refusing to back down after it was obvious the decision was a poor one. He was a proud man, and in many cases, that pride hurt his company's products. Ironic, since the perception of his company (and him), was product quality based, and that had nothing to do with whether a good (or more often bad) idea was his or not. It was that many games went rotten, and although they, in many cases, could be fixed in time, he just wouldn't back off once he had made up his mind.
(B) (more of the time) Projects are rushed. This happens alot -- many projects take longer than expected, and the publisher doesn't want to throw their money away by canning the game... so they force the game out the door way too early, and attempt to recoup their losses, rather than gambling on the developer creating something fun, with a few million more $ down the tubes. You can't blame them, really. Many higher-ups at publishing companies don't really know what makes a good game different from a bad game. They see sales numbers on titles the developers have told them are direct competition, and listen to producers spin how great game X is going to be. They have no way of telling "oh, this game could be better if it just had a little more time" -- they hear it from their subordinates, but... after a while, they get scared, and shove the game out the door whether its ready or not. The games industry is cutthroat, and if you're in a position of power, and you're looking like you're throwing the company's money away, you're going to get a severe beatdown from the stockholders, and/or lose most of what you own, by watching your own stock plummet. Pushing a title out the door and crossing your fingers probably seems like a good option, in a lot of cases, especially if you have no idea, personally, if the game is actually good or not.
Yes, the games industry is that immature, such that textbook economics don't teach much about how the games industry actually works (and in many cases lead execs astray in their decisions), and the industry is so brutal, that the number of good, knowledgable execs that survive the ranks to make it to the top (before leaving the industry, because its exhausting) is *very* small.