So, as of your question and after having a look in my play store there is an option indicated top games and apps for 2015. so these are Top 6 Android games for 2015.
1- That Level Again
With 1 million downloads and a rating of 4.5 is a quite popular one. It is a Logic game where the game being the same, but the winning strategy will be varying. With 64 distinct levels, this is the best one so far.
2 - Marvel Future Fight
With a whopping amount of 10 million downloads and still a rating of 4.5 is quite an impressive.This game will let you go to that all the Marvel hero's and unite them. With the updates, new characters will be introduced.
3- Stupid Zombies 3
With 1 million downloads and a rating of 4.5 of an old fashioned Zombie game. Involved with Geometry and weapons of different categories, this is a fun and action packed game.
4- Criminal Case
I think this game needs no introduction and with 50 million downloads and a rating of 4.5 is the award-winning crime investigation game in the play store.
5-Inside Out thought Bubbles
With 10 million downloads and a rating of 4.4, this is a bubble shooter game based on the Disney's "Inside Out ".With much more game events and will be a fun loving game much like candy crush.
6- Heartstone Heroes of Warcraft
Much like this game tagline' Deceptively simple, Insanely fun" with a 10 million downloads a rating of 4.3 this will be a mind stormer for the players.
All these games are available in Android play store.