The best way to come up with ideas for games is to play games. While playing a game, think about what YOU would have done to make it better or a feature that you think you could improve on.
Another popular thing these days are reboots of older games. What was your favorite game as a kid? I liked a game called Fantasy Empires that had a lot of original ideas in it. There hasn't really been a game like it since it came out in 1993. I think a modernized version would be awesome.
I also have ideas for games based on books, movies, or tv shows. Want to create an RPG? Read some fantasy novels. A zombie game? Read World War Z.
You can't really search for inspiration, it just sort of happens when you are least expecting it.