[youssefbasha]

COLOR OS IS ANDROID FORK . NOT ENTIRELY ANDROID OS . color os is an android fork that is used in shitty oppo phones . those phone is just care about front camera , almost all their phone have really shitty specs for high prices . because the money goes to the sales that sell oppo phone enough about that basically it is android but with modified UI like MIUI (used in xiaomi and other phone that support it) , Oxygen OS (used in 1+ device) , Funtouch OS (used in vivo (oppo spinoff) device) , etc

and forked os mostly contain different ui than stock mostly better UI and more feature than the stock ,

and for the best gaming os it is hard to choose iOS on the other hand have better optimization but android have more flexibility and also the os itself is more open that mean you can easily install mods but for most people android is a better choice . considering that android is much cheaper than iOS

Sorry for late reply, 
Android is much cheaper and you are right but as i think that android have bad points as it may get hacked / you can download any applications for free (paid applications) <cracked> but at iOS you can't install paid apps for free and iOS is smarter and smoother than android.
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While, @sagher

Also huawei used additional EMUI UI interface. but they worked so smoothly.

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EMUI is good but it doesn't get update. 
I have a Huawei T1 (Tablet) and it didn't get update till now (from 1+ year)