Nintendo originally announced Super Smash Bros. Brawl sometime back in 2007 and changed the date of release to about a year later. I remember being so excited to hear about Brawl, then was pissed when the game kept getting pushed back farther and farther. I think it took so long because of the drastic changed between Melee and Brawl. Brawl seemed likr an entirely new game to me, and still does. At least Smash 4 seems a bit like both which is nice.
The push wasn't that long, and the reason for it was because of the sudden request to add Sonic in at the last minute. Characters take a LOT of development time.
Aliens Colonial Marine is a really good recent example. What an abomination. Another infamous example is Sonic 06, but that was more of a rushed development. Metal Gear Solid V is a pretty good example as well. Though not a bad game per se, it really suffered and could have been much more...well, not really, because it was too ambitious. The game ended up a disappointment more than anything even if it's still fun.
Hilariously I have more examples of games that underwent development hell but ended up incredible. (Metroid Prime, Metal Gear Rising, Mother 3, Team Fortress 2, Bayonetta 2)