Let's remember that LGBT cinema is still a small genre. When content providers are putting together an LGBT selection, they have a much smaller collection from which to draw, which means that more of the schlock is going to be found in there. There are tons of crap films pumped out every week in the DTV and MOTW industries, but they die in the face of better alternatives. LGBT schlock survives
longer because the catalogue is shorter. That being said, I think that there is already a corpus of good, even great, gay cinema out there.
I will leave it to one of the women here to bring a more knowledgeable perspective on lesbian cinema. I am not at all sure that bisexual cinema is well developed yet, but again, I don't think that I am in a good position to judge.
I suggest Lilies, Love! Valour! Compassion! and Edge of Seventeen (for the soundtrack alone!) are all good places to start.
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--James