People have different views, but I completely disagree with you. The writing of the script, obviously took a lot of effort and a lot of hard work. In my opinion, it surpasses the Cing games' storylines such as Hotel Dusk. I know you have an opinion, but I greatly suggest you play the game to actually get a feel of how good the storyline is, it's one of my favourite DS games.Maybe 999? Got hyped up pretty hard on the internet, then when I check it out it's a poorly written point and click game. Maybe I didn't get far enough to see how good it could be, but that writing was so bad. It was like a 12 year old writing fanfiction levels of bad.
I could probably think of a ton of other games I was disappointed in, but that's the main one I can think of. I usually love that sort of game, too (the Cing games on DS, Broken Sword, etc)
As for my most disappointed game, it would probably be Bleach 4th, the previous games were great, but this...