1. If its a romance game, it better be deep just like what Radiant got right, everyone cared for the mother of MC's three daughters that its almost a common comment "I cried when I heard the mother of the daughter's died" or "This game hit me on the feels".
2. Write a consistent and believable character, I played Sunshine Love but instead of being enjoyable it just made me feel angry with the main characters. Also follow Palmer's example, the story is shit only thing decent are the girls.
3. A story that won't make it a fuckfest or make you want to hit your head againt the wall, what I mean is believable and compelling as others above said. No stupid cliches like: seeing a guy's penis and then after a short time get fucked by said penis UNLESS its an established relationship like MC has a girlfriend/wife.
4. Also if you add NTR whether it be optional or the only thing, you better put it in the tags. Also many people including me don't like sharing the Love Interests with other men. Just check Summer with Mia thread, unavoidable sharing because of "story" honestly if Inceton wasn't established he'd be losing patrons, he just justify it because he has a strong patreon following. But its common that NTR only games eventually become an NTR avoidable game because of lack of support or no growth in the support, its actually pathetic of them.
5. If your game has no NTR to begin with do not pander to the NTR crowd, you'll only get backlash.
6. Also be patient if you don't get much support right away. If a significant amount of time passes and it remains so then I suggest you check what went wrong, and if need be put it onhold and make a different game.
7. If you could, make your game have its own identity. People don't want a Milfy City clone, a Big Brother clone, Dating my Daughter clone or be clones of other popular games.