I always try to play in the author's / dev's native language if I'm fluent in that. Things get lost in translation, so the original is usually the best.
If not, I default back to English. Because English is such a wide spread language that it's usually the best (or the least bad) translation.
I play AVNs in my native language if and only if (1) it's the original language, and (2) it is actually at least as good as the English translation.
(1) is almost never the case. (2) has not been a problem yet.
I normally play AVNs in English because that's normally the best language available. But I speak several languages, and if one of the others (1) is available, and (2) is better than the English version, and (3) the English version is bad enough to make me check this, then I will play in another language that is not my native language. So far this has not happened because each of the three steps is actually quite rare despite my languages being quite common.
I wish I hade a more common language that gets translated to more often. Luckily I live in a country that is one of the best english speaking ones in the world (for a non-english speaking country), so its not something i really need. I just think it would be fun to beat my meat while reading sex dialogue in my native tongue sometime though.
English is my family's mother tongue. Like that old joke I speak English and bad English. American English is not proper English, but it is all I know. Except for some British spellings sometimes I fall into or British colloquialisms. I always play games in English of course. I've played raw Japanese games too though. With no translation not for Visual novels though, JRPG.