Ah yes, the "Other people are enjoying a kink I don't so I am literally turned off now." Seriously, there are plenty of non incest games. Is incest a big market? Yes, it is. However it isn't the only thing here. In reality, the thing with incest is it's an easy kink to write, because really it's just sex. What makes it easy is the drama created by the taboo, which allows you as a writer to explore the characters thoughts and feelings.I don't, and frankly this sites seeming obsession with them is something of turn off.
There aren't many kinks that are that easy. You might be able to accomplish something similar with a teacher student game, but then you run the risk of getting into the under 18 territory, which in spite of the fact that they're cartoons, makes governments freak out.
If you ever need a good list of games to play without incest, pop over to game suggestions, I'll help you out.