For those who feel like a side project needs to be successful or reach a certain amount of revenue/lines of code/users to be successful in your eyes: Don't feel pressured. In my career (granted not a long one, but made it to C-Level in a startup after about 5-7 years) I've always used them to show my interest and learning skill to do something. It didn't matter whether it had 1 user or 1 million, employers were alway…
What's your path from developer to C-Level? I feel like the companies I've been at don't really let developers move up to management positions, unless you come from the outside or somehow gained management skills somewhere.
Developers (or PMs) who are interested in the business they work in and participate actively tend to get promoted/pushed. You have to understand the business perspective if you want to move up and get away from the thought of "I'm just here to develop and if I make the product great, everyone will recognize my talent/skill"