Fun, sure, but not an experiment that would actually be meaningful.
The data from your phone’s microphone doesn’t magically appear in Google’s advertising servers. It would have to go through a lot of steps before it gets there, and one of the first steps is in your home (if you’re on WiFi). One can analyze the traffic/data that leaves their phone.
It’s good to be cautious, but worrying about your phone’s microphone is potentially like worrying about your windows while leaving your front door open.
That’s awesome. The Dreamcast was the first console I played online.
Ooga Booga was a great game, and would probably still be fun today if it had some players.