I'm honestly surprised there isn't even a fan translation of the TTGL manga with how popular it is. Or the basketball parallel universe manga for that matter too.
I might try and ask Trigger sometime if it's possible for the mangas to be localized, though IIRC a lot of that is often in the hands of people in the West too.
At the very least we are now seeing GaoGaiGar getting the love it deserves. Every time mecha comes up when I'm talking to friends IRL I'm like "have you seen GaoGaiGar?" and the answer is almost always "I've never heard of it."