So, are you looking for characteristics used in games that you could implement in your game?
Personally, a juicy plot always draws me in. Of course, there has to be a good amount of choice-making, as it’s an IF. Having developed characters always helps too, because I love having characters that I can connect with- they’re pivotal to a story. (It’s also nice to find a character you really like and can romance 
)
Or even if the story is told in a unique way, like how Choice of Dragons starts out. So basically the main selling point for me is the story.
(I also really appreciate good grammar and spelling in a story, too, lol)
As for character customization, I found this thread a few days ago: Customizable appearance: How important do you find it? - #11 by BoltSterling where people gave their opinions on customization’s importance to them. I for one like having at least basic customization, as it helps me cement my character in the game.
Replayability is…a really interesting thing. Most CoGs I don’t replay right after I finish- I might decide to play it again months later if I loved the story. But as long as the story was fulfilling and left me satisfied, then replayability is not an issue and I’d call that a great game.