1) get an idea for a cool app
2) evaluate feasibility and execution
3) ensure accessible data streams and APIs
4) get excited and realize the idea is doable
5) see someone has done that exact thing and it's already published on the Appstore :/

Good! Now, you know what's the first thing you should do when you have an idea.

You could make it anyway. There were plenty of chat apps until WhatsApp came along. Google wasn't the first web search site ever. Slack is not the first communication tool. Make it better or sell it better, and yours can still be the successful one.

This may be better:

1. Get an idea for an app
2. See if anyone else has done something similar.
3. if (they have) {
look at their reviews and see if you can take the complaints and iterate and solve the issues.
} else {
Validate your idea on some friends or better yet, the target market of the app.
}
4. Build it if value of step three validates.

Do it better. Google wasn't the first.

6) check what issues has the published app
7) improve your app with the given feedback
8) publish the app anyway

Use the already published app, see how you can improve it (at times you will even find better ideas from using the app), then implement it.

1) get an idea of cool app
2) serch hard if anyone have done it already.
Time is saved.

It is actually a good sign when you found a competitor. It is much worse otherwise. The next question should be this: how is popular this app? Can you make it better?

@rehman thank God your not involved in companies like Google.

@W1ckeD I see what you did there.