"He is usually angry."
一般 and 经常 can both be translated in English "usually." 他经常很生气 means that the person gets angry easily but somehow the status of anger will end. but if you say 他一般很生气 means that he has a constant status of being angry and seems there's not an end which is kind of weird.
besides, i don't think this chinese translation is good enough. "他经常生气。" is better then "他经常很生气。" . "很" means "very" in English, but I don't see the hint of "very" in the original english sentence. And "他经常很生气。" sounds weird in Chinese too...
We use 一般 to describe the habit instead of emotion. It's better translate "be used to". I'm used to get up early. 我一般很早起 Also you can replace 通常、經常. But if you use 一般 to describe the status is inappropriate. Actually, this sentence isn't like the native, I will say 他經常生氣 or 他很常生氣 or 他常常生氣。