Since this is a hobby project, pick something you want to do. If you are motivated, it will be easier to pick up the skill you will need.
Beware of projects that require a lot of art and content. Things like adventure games etc. consist for a disproportionate amount of artwork and level design. Especially for a developer starting out, these can be the kiss of burn-out death.
Pick something with a defined scope and measurable goals in between. The sense of accomplishment you get from finishing every little milestone along the way will go a long way in keeping you motivated throughout the project and into the next.
For me, this advice led to re-creating a 3D version of a popular 1980s game. But your interests are different, so you will most likely end up somewhere else.
I would say, think about it for a while and come up with the simplest possible project that you still find compelling. If you need assistance figuring out what technology/platforms to use to make it, just post another question. We love arguing about technology around here ;)