Oh, I thought of a new one...but its kinda related to an old one I already posted.
Console ports of Ultima games. Ruined by Ultima V: Warriors of Destiny for the NES. Seriously...what the fuck happened? Ultima IV for the NES was fucking STELLAR by the standards of the day...hell, it was the first video game I'd ever played, and I loved every minute of it. But, Ultima V was just terrible. The controls were clunky and very, very slow to respond...which made the new, real-time combat a major, MAJOR pain in the ass. And the graphic design was just an eyesore, at times. I mean, take the Avatar him(or her)self. Sure, he may not have been very detailed in Quest of the Avatar (this -is- the NES we're talking about, here), but in Warriors of Destiny...he was just a deformed blob of red and yellow.
Would it have been so difficult to just take the general look and feel (and story) of the PC version and pop it into the NES engine for Ultima IV? Touch up the graphics a bit, sure, but...Jesus. That game marked the end of good console ports of the Ultima series. Ultima VI for the SNES sucked. Same with the SNES version of Ultima VII, where the game in general, and the story, was just plain butchered because not only of size restrictions (paring a 20MB game down to 1MB does that), but also because of Nintendo's shitty censorship policy...MURDER IS SCAWWY!
Oh, and the fuck of the Ultima VII SNES port? That's the version they used for the PSP port. You read that right, instead of using the, by that time, small 20MB proper fucking game, they used the bastardized, piece-of-shit version that fucking EVERYONE hated. Good going, Sony. Fucking dumbasses.