I agree with moeen k. Play some mobile games yourself, whatever games you like to play and get some inspiration from those. Think about what you would like to see in those games or what they have done wrong and how you can improve it. That's how I got the idea for the game I am currently developing.
Develop a game that you would like to play. If you don't want to play it then others will not want to either.
Good luck and keep us posted.