I've been playing games since I was around four years old, and started writing my own not long after. This was on the BBC Micro -- I played a lot of Elite, and loved it for the sense that you never quite discovered everything.
I've always had this urge in me to build things. Besides the computer, Lego was my favourite toy. As a result, construction games like SimCity and RollerCoaster Tycoon were, and still are, the ones I love the most. And I guess this urge extends to building games themselves, rather than just building inside the games. My dream is to create a proper construction/engineering game of my own some time :)
The inspiration for the games I make often comes from daily life around me. Rocket Mail was inspired by long-haul air travel, when I noticed how maps deceive us about where places really are. The construction game I'm thinking about was inspired by a construction site across the street. And so on.