[1] https://www.fgl.com/blog/2015/11/fgl-to-drop-support-of-cert...
[2] https://www.fgl.com/blog/2015/11/fgl-will-no-longer-support-...
Also, I wouldn't judge popularity by money made through ads. The industry has long since shifted to in app purchases.
https://www.facebook.com/games/query/top-grossing/
Edit: Also, I believe Kongregate has a whole ton of games with In-App Purchases. I don't have any experience publishing on there but I do have experience on Facebook.
http://www.businessinsider.com/facebook-payments-revenue-dec...
3 things
1) it's a platform: the flash platform
2) inside this platform you can find many runtimes: Flash player, Adobe AIR, Redtamarin ( https://github.com/Corsaair/redtamarin )
3) you program those runtimes with a programming language: ActionScript 3.0
as long as there are runtimes to run programs it not gonna die
enjoy ;)