Forgive me if I'm stressing this too much, but I believe that one of the primary goals of this project should be to encourage and facilitate a community by creating a game that is easy to create/mod content, easy to upload and download player created content (so you can share with your friends) and perhaps even has some sort of central repository where players can browse, submit, download, and rank the player created content.
With that in mind, what are some types of games that lend themselves well to a community like that?
With TD games you could have player made maps, perhaps even customized campaigns and challenges (e.g. "survive 50 waves with only 5,000 resources," or "Only use gatling gun turret," etc.)
With puzzle games players could create lots of different puzzles. Depending on what kind of puzzle game and the main gameplay mechanic behind it, there could be room for lots of variation (again, think of
ChuChu Rocketw (or
RUSH),
The Incredible Machinew, Portal,
box-pusher gamesw,
Lemmingsw)
It could be a relatively simple platformer game (
Super Mario Bros.w or
Within a Deep Forestw) with a level editor. Again, you could have players created individual levels, entire customized campaigns (a series of levels) or challenge courses.
It could be more of an adventure style game (like the old-school Zelda games) with customizable world maps and dungeons. We could (eventually) have a huge DC world where everyone gets to contribute a section of it and a dungeon or two.
That would be fun, but probably pretty large in scope.
Could have a Worms-alike, but I don't think there's a whole lot of player-created goodness involved. You could make your own stages, but personally I don't see much value in human made stages over ones that are randomly generated.
It could be a (
Mode 7w style) racing game (e.g.
Super Mario Kartw) with customizable tracks and circuits, perhaps even customizable battle arenas as well.
As I mentioned before, it could be some sort of sim where you can build a city or whatever and share or visit other player's creations.
Arcade-style games (Pac-Man, Bomberman,
Mario Bros.w) with customizable arenas. Though these arenas would run out of variety pretty quick, it seems.
Well, that's about all I can think of for now. . . (and most of that didn't even touch on multiplayer).
But anyway, the point is, in order to facilitate a community around the game and project, we'd have to make sure there were easy to use, intuitive tools to create the content with. That means we'd either have to create such tools ourselves or find them already made. The good news is that having such tools will make it easier for us to create the "main" content for the game as well.
Also, once we have an idea what kind of game we want to make, then we can start focusing on what engine to use, as then we will be able to select the one that fits our requirements the best.