An open world rpg like Gothic is what I always wanted to create. That will probably never happen
I focus on small games instead. Even though I’m learning to implement some typical rpg mechanics right now.
I like systems, simulations, procedural content, atmosphere and human interactions. So something which combines those five elements. Predefined stories are a big no no. And yes Steam would be nice.
Another idea: a spaceship game where two automated, AI-controlled replenishing huge fleets fight, MOBA style. The player is NOT a fighter ship, but a supporter, trying to help his team with non-combat actions (scavenging materials, transporting goods, mining, scouting…), all that while avoiding or dodging the enemy.
Apart from my current project, several ideas that are way out of my league until I have more experience and some fellow developers on my non-existant team. Still have hopes for my Privateer/Crimson Skies mashup and a kind of XCOM clone in the Mass Effect universe (legal issues aside of course).
Also, ideas got thrown around of a Lemmings/Blade Runner mashup where you had to guide a couple of mindless androids to the exit while keeping them safe from the anti-robot riot groups. Androids could be assigned different tasks via punch cards you had to collect, and sometimes a card’s order could burn into the android’s brain so he wouldn’t accept any other commands after that.