For years, SwiftKey soared above Google's included keyboard, and it did — and still does — come pre-installed on many a phone and tablet. SwiftKey's prediction methods, called the "fluency engine," has made it the keyboard that many users and editors alike keep coming back to. SwiftKey has been pre-loaded on millions of devices over the years, including on Samsung's flagship phones.
While SwiftKey used to be a paid app, the keyboard itself went free in 2014, instead having its users pay for themes. SwiftKey has led the keyboard pack for a while, and was our readers' top response when we asked which keyboard they used. And it's still a great option in 2016.
Bottom-line: SwiftKey is a great option for those looking for an alternative to the stock Google keyboard.
One more thing: On the topic of themes, there are over 80 of them to choose from in all sorts of colors and styles to fit your personality.