Ugh, there are so many ties for most boring game ever in my book.
Runescape: Ugly, boring and tedious.
Any Metal Gear Solid game. The story makes no sense, the combat is poorly executed, and even the characters tend to feel as if even they have no idea what the hell is going on.
Hellgate London. It felt like playing a MMORPG, but unlike Warcraft, it was boring and stupid. To many 'Go collect X amount of objects or kill Y amount of monsters or find some random item which you pretty much have to walk all the way to the moon to get' quests without having a semi engaging backstory like WoW.
(Yes, I know WoW isn't everyones cup of tea, but I enjoyed it, so please don't quote my reply saying stupid crap like "LOL, WoW was teh booring! I hateed it, U should die LOL!"
Any JRPG.
Azurik: Rise of Perathia for the Xbox.