- Sometimes dubs entirely change the intended personality of a character. Somethings don't translate, you don't even need to know the language, ever watched a foreign movie dubbed? no? Imagine Tarantino made all the scenes in Inglorious Bastards in English instead of German with subtitle? Do you think it would feel the same? nope, not by a long shot. It's like that for most Japanese games too. Specially all the 'cute' and comical scenes just come off horrible in English as the voice actors usually can't covey the same thing.
- There is no lip syncing at all, making it all more jarring, or lines written and forced to the original lip syncing.
example: The 3rd Birthday
- If you've seen recording sessions of Japanese voice actors, they actually often are in the same room and act together for a scene, while for English dubs it's not common at all, mostly actors don't even meet each other at all! That's why performance capture is becoming more popular, because the actors actually play the scene themselves and say the lines together.
example: look for FFXIII interviews with voice actors, they didn't know each other until the game was done... it's not really specific to this game, this one is just more public.
Good enough reasons to me to demand dual audio. But again there are some games with dual audio like Ni No Kuni that has changed all the names in English transcript making the Japanese VA useless. There are lots of cases like that there is a big difference between what is said and the subtitles and if you understand the language making it pretty bad to play like that.
And at last, I think there are dubs that are superior to the original but it happens rarely. Like FFXII. I think British English is better for Japanese game myself, it works better. Resonance of Fate is another good recent dub in American English.
It's not really specific to Japanese games, English isn't my first language but I play games in English all the time and not the localized one, voice or text. Because it's awful mostly compared with the original to me, and there are often a lot of spelling errors and alike...