Localizations (the best and worst)

[Dolphman]

Nintendo of America, until the Gamecube and Wii, had a bad "family friendly" policy where anything got butchered for censorship.
The first Mortal Kombat for SNES is considered the most inferior version of all the ports because they censored the crap out of it.
Sega one the other hand, had the right idea by having a parental lock system on the MegaDrive version, via a cheat code.

It was this policy that lead to a lot of companies stop making games on their systems, and moved onto supporting the PlayStation more.
And this is still in affect to this day as they don't even port some of their new games on Wii U. Mostly due to compatibility issues.
This will probably change once the next gen consoles come around, which will be a while as the current ones are still young.

As for "cultural modifications". I think Awkward Zombie said it best with this comic mocking Ace Attorney's English version.

It's lucky Yo-Kai Watch is still set in Japan, but it's still jarring with a few things. Like Komasan and Komajiro's hillbilly accents.