Amazon app store is the best alternative to google play store. Fee for creating a developer account is free before it was 99$. Google Play Store has a one-time fee of 25$ for creating a developer account and for Apple App Store it’s 99$ per year.
On Amazon App Store developer can set a free app to paid app later, while in Google Play Store once the app is set as free it cannot be changed to paid app later.
Itch.io is a marketplace for independent video game developers Itch.io is released in 2013. By default itch.io takes 10% commission from developers each sale, but developers can set the commission rate for each sale. Itch.io supports Flash games, HTML5 games, Unity, Android, IOS and other downloadable formats.
The developer can include his game link submitted in other App stores like Google Play Store and Amazon App Store on Itch.io game page.
SlideMe is the another best alternative to Google Play Store. It is founded in 2008. Unlike Google Play Store, SlideME focuses on quality than quantity. The fee for publishing apps on SlideME is free, the payment system supports the PayPal, Amazon, and SlideME Wallet.
Opera mobile store has 10 million visitors per month. It provides over 2,000,000 apps and games for more than 7,500 different mobile phone models across most platforms: Android, Java, Symbian, BlackBerry, Windows Mobile, and iOS. The developer can submit Android, IOS and HTML5 apps.
For creating a developer account on BlackBery user need to register first for BlackBery ID and then a BlackBery vendor account for publishing apps on BlackBery store.