Get random with it. I also had that same idea with the dice. I made like 3 categories and rolled 1 time for each. I would get insane creations that sounded absurd to the max like Football + pacman lol. Or even Monopoly + Bioshock. XD
I find i come up with fun ideas when i'm not stressed. Usually they come to me when i'm not trying to hard which is odd.
Ideas also develop over time. I'm making a cow game and it originally started as a bedtime story for kids involving a common rhyme that goes like this " Hey diddle diddle, the cat and the fiddle, the cow jumped over the moon". Eventually my idea mutated into a cow saving his family from evil aliens from outer space.
Children's books are a gold mine my friend.
Nothing is to unrealistic.