Monster Girl 1000 is the only non-renpy game I know that fits the description. And you're not literally the only male in the world, but basically life is about to go extinct unless you start sowing your seeds.
Just putting some renpy games here as honorable mentions
Giant Guardians There are actually plenty of males around, though I can't recall one even appearing. It's just that you're a pure human, making you extremely desirable for breeding to the point where many of the giantesses go crazy and want to kidnap you. This does contain things like gore, death and vore, but it's very obvious which choices are more extreme.
Lust Age Only guy in the whole village, generally low male population because of a curse. You're more a protector and need to play by the rules, so no rape or reverse rape, but everyone still wants a piece of you.
Goddesses Whim Only guy in two villages because reasons, similar to lust age.
