Something that I see mentioned a lot in this thread is branching paths. As someone who is creating a game with major differences depending on which of the 3 (now 5) main paths you choose, I have to say it is a pain in the ass.
With regards to creating a story I wholeheartedly agree. Too many games are little more than fleshlights. It's something to jack off to but afterwards there is nothing there for you to enjoy. So you close the game after you nut instead of wiping yourself off to see what else this game has to offer.
I will say though that a new wave of story focused games are arising. Melody, Acting Lessons, Lexi (shameless plug). After the success of Summertime Saga brought more attention to this side of development. I was surprised to see fairly famous NSFW artists jumping on board the AGD train like Boobsgames,David Goujard (old hat), sadi. Freaking Grandpappy Akabur and Sunsetrider7 are now pioneers in something that will undoubtedly break into the mainstream soon.
But if I could impart any one thing to new devs it would be this; Make believable people.
So if you create a character, don't spend all the time on how they look. Take some time to think about who they are. People can tell the difference between a fuckdoll and an actual character. The sexdoll lies there limply after a good time. A character continues the experience after sex. Just because you fucked, doesn't mean everything has changed and you are finished with this character. Give the player a reason to want to keep fucking rather than move on like a heroin addict looking for his next fix.