Sonic 2006 is the only game I completed that I can safely say was pure dog feces. OK, maybe not completed, but I did beat the final level because my brother hilariously gave up and it was awful. I do not want to touch that game ever again.
It's not even just the gameplay that's bad. (It's comparable to Sonic Adventure which was not as bad but still pretty bad.) The writing, presentation, story and the new characters were all pretty cringe-worthy. :( Level design and quest design make me want to rip my head off too. The only thing GOOD about the game that I can even think of was it's music, but it was forgettable because the game makes you want to forget about everything related to it.
And curse you, I liked Super Princess Peach! Though I haven't played it for a long time so I want to give it another spin after I play Densetsu no Starfy 3 which is from the same developer. You know one game that is mediocre on the DS though? Wario: Master of Disguise. I think my bias towards Wario really shows off when I say I actually personally like it, but there are way too many flaws about it. So I guess that's one bad game (I'd like to say mediocre, instead, since the concept of the game is really nice) I like. The other guilty pleasures of mine are Mario Sunshine, Super Mario Land and the DS remake of Mario 64. (Looove them. <3 Super Mario Land was my first Mario game!)
I always find it nice to go back to the old, classic games of Mario/Sonic. Really makes me feel like a 6-year-old, since those are the sort of games I played back then. 'Twas a good year in my life. :3
Fun fact, I actually thought those who preferred 2D sonic back then were nostalgia people. Guess what happened when I played Sonic 2 for the first time? Favorite Sonic game. I started Sonic with Sonic Heroes, if you're curious.
Another b-rate game that is absolutely amazing is Disaster: Day of Crisis. Its almost so b-rate that its likely intentional, and I love how the game progresses.
I know nothing about Disaster besides hearing about how good it is but I want it just so I don't regret it later when I move back to an NTSC region. The only other PAL-only (NTSC-J aside) game I have is Another Code R (brilliant), and I guess The Last Window. (but it's region-free so it doesn't count.) I also have some games that never made it to PAL land like Trauma Team, Mario Super Sluggers, MLB 2K12 and Jake Hunter, and probably some more I'm forgetting.
Only Japan-only game I have though is Rhythm Tengoku.