Serious answer: No one can give you a good idea, because the most important factor in what is a good idea is what you personally are most passionate about. Any idea can potentially be turned into something fantastic as long as you care about it enough. (I wrote an effort-post on this once that I spent ten minutes trying to find and couldn't. Oh well.)
As far as finding out what you care about, start thinking about what works of fiction you enjoy reading/watching the most, and see what they have in common. Genre? Are there certain themes, plotlines, or character types you always love? Then see if you can unite those ideas into something that means something to you.
Start thinking about what conflicts in your real life matter to you most, and possible ways to fictionalize and dramatize them. (Though be careful not to write a self-insert; doing so prevents you from being as objective as you need to be about your story.) This can be personal things like career anxieties, drama in personal relationships, or health struggles, or more large-scale impersonal things like worries about some political issue, an exploration of what redemption means, or existential reflections about whether humans are alone in the galaxy. Any topic that you feel you have something to say about can be a good throughline for a story.
The best story ideas come from combining multiple independent ideas that interact in an interesting way. Ideally you'll come up with some external conflicts to pair with some interesting characters and emotional centers, all of which should be based on core ideas that you, personally feel excited about.
You'll know you have the right story idea because you won't get bored of it quickly, and you'll be excited enough about it to take it all the way to completion.
