Even when PES was at its peak, it never outsold FIFA. Its fan base will always be small compared to FIFA as it is not for casual players. There is a learning curve involved and it isn't exactly pick-up-and-play. That being said, even during it;s worst sales period it sold 4 million units, which is not a small number. And more sales doesn't mean its a better game.
It was, at one point, the top dog in football simulations. They were so good that they didn't feel it needed to buy Fifa 16 coins. FIFA then changed their approach to the game, making it easier for the casual gamer to pick up, so it became wildly popular. Change is always the name of the game which is why a lot of people are getting fed up with FIFA currently. Just my two cents
I've spent at least 10 hours sniping players in FIFA since price ranges have been introduced so if I spend 10 hours modifying PES names to make it better then I will. I know this is a FIFA subreddit so of course people are going to be biased and will probably be downvoted.
On PC you just run patches made by the community which edit your game files. On X360/PS3, you just download a few files made by the community and put them on your usb pendrive and move them on the console. On X1/PS4 you can't do that but in PES16 for PS4 you'll be able to import images from a pendrive and use them ingame, making the process harder but you will still be able to play with all licenses.
For me the reason i buy Fifa is mostly for the online 1 v 1 gameplay. I have heard horror stories about having even worse servers and shitty connections on PES online. Me and my roommate used to go super in depth on Winning Eleven adn create our own team, own kits and build up our team throughout the years. but that was offline, and once online became more popular and fun for me i switched back to Fifa.
The only "bad" thing is MyClub, which is honestly not as good as FUT but has a few cheap Fifa 16 coins (when playing offline you just play against someone else's squad controlled by the game, you can play real time competitions where you qualify for a tournament if you are among the best 16 out of 3 matches, player chemistry becomes better the more you play, you can let the game control your squad in simulated matches)