HALO!!! Goddamn, I usually love shooters, but the Halos are just so f*cking boring. Same hallway, random monster appearance, repeat. Ditto for Doom 3.
I've tried a lot of RPGs, but can never get into them. It's not so much the gameplay as the setting. I love the KOTORs and Fallouts, but anytime an elf comes up to me and says "Welcome ye travelers to the precipice of mount seamus's wang" or whatever, I throw up a little bit in my mouth. I just don't like fantasy. (On that note, movies that were totally overrated IMHO = the LOTR series. Please don't kill me, fanboys)
Other than that, I'm sorry, but I just found Deus Ex very cumbersome. I can appreciate the influence its had, and looked into the story later and quite enjoyed what I saw, but the interface and AI really got on my nerves.
Oh! One more thing. I didn't like Prince of Persia either. Fun for about 3 minutes, then you've seen pretty much all the variety you're gonna get.