Here are a list of really shitty ones I've actually tried to play (not beaten all, or even most, of these):
Oblivion (I saw an unfinished game the other day, horrible creatures.)
Dungeon Siege (Almost a stretch to call it a game, since it plays with itself more than you play it)
Dungeon Siege 2 (Tries some new things. Fails horribly at all of them. Tries to do Bioware style party banter but it always gets interrupted by combat and broken, combat is shitty, party limits based off of diablo style difficulty levels is retarded, list goes on.)
Mass Effect (Shit RPG and shit TPS.)
Dragon Age (Last Bio game that tried to be an RPG. Failed at it. So many trash mobs, such shitty characters, why the hell does a character as retarded as Morrigan exist? List goes on.)
Arcania (Unplayable mess of fetch quests and broken combat with retarded stunlocks.)
NWN2 OC (This one was just really, really boring, and tops it off with some of the most retarded camera controls I've ever seen in a game.)
NWN OC (That is, if we are considering only the OC and not the whole package, lots of fun was had with modding and persistent worlds and stuff with SoU + HotU. Doesn't keep the OC from being trash though.)
Nightstone (This is a really terrible Diablo clone I had the misfortune of owning as a kid. Think it still lies in a box somewhere around here.)
Might and magic 9 (Everything is wrong with this unfinished mess)
Lionheart (starts promising, quickly wanders into the dreaded "shit-tier Diablo clone" swamp.)
Konung 1 (Horribly broken game, some codexers seem to consider it decent. Almost falls under the category "shit-tier Diablo clones". Can not understand those codexers' point of view. If you think the infinity engine had terrible pathfinding, you are in for a treat as you spend minutes getting your guys to walk across a bridge in Konung rather than getting stuck on the edge of the cliff.)
If jRPGs count, I can name more, including but not limited to:
Grandia 2 (Owned as kid. Sucked.)
FF8 (Grindy as shit. Story sucked. Characters were knee deep in shitty writing.)
Legend of the Dragoon (Game just generally sucks. Retarded QTE combat doesn't help.)
I'm gonna get flak for this from the resident weeabos, but Persona 4 also gets an (dis)honorable mention. There are some things it does well, but that doesn't excuse the retardedly broken combat and RNG dungeons. At least Arcanum combat is generally fast. P4 combat isn't. It's like a lot of the things that were really good with P3 got taken out and replaced with retarded shit. P3 uses a fatigue system to encourage breaking up the dungeoneering, as well as the fact that it doesn't force you to waste day blocks. P4 basically encourages you to take on the whole thing at once to unlock your social links and not lose time, which is retarded. P3 dungeons are also less retardedly broken.