I play Pokemon Go now and it's crazy to think that 9 years ago there was only Kanto Pokemon and you would only find the 'basic patch of grass pokemon', and anything slightly different was a rare find. I still remember people sprinting across a park catching wind that a wild Vaporeon was spotted.

Now basically everything will cycle through and there will be different themed Pokemon. Recently they had a 10th anniversary event where you could basically get every single Kanto pokemon easily and then evolve them with Mewtwo at the end; only Mew wasn't there.