If you like fantasy style tower defense games, Castle Defense delivers that and a bit more. From the beginning, there is a story line progression where you choose a character to fight against the hordes of evil. But don't think of it as a game that would win you over with just that.
The four towers come in the three generic TD versions with one exception: the cheap arrow tower, the slow splash cannon, the slow tower, and a chain attack tower. These towers can then be evolved into further specialized towers.
There are also achievements you can get from playing the game, if you are interested in leveling up your Google Play score. But as the game has a ton of in-app purchases, it also has a ton of ads. So if you don't mind getting 4 ads popping up before playing, feel free to try the game here.
Otherwise, check out number 5 on our list, Kingdom Rush.