Simulation platform? Yes, platform. A game (which is a simulation) consists of so much more than code. You also need gameplay ideas, graphics, sound, etc. Also, the code should be modular in such a way that its independent of game type, so that the basics to create a game are there, but you can mold it in any way you like depending on what you're creating.
First, we should create a website where users can dump their art, others can improve it, and everyone can freely download it. All content posted on the website should be licensed very freely. In this way, someone with an idea does not need to worry about creating dummy meshes to test his idea, but can simply go to the website to grab the things that roughly matches his imagination.
Second, we should create a modular simulation engine. The core should only know how to start the application, load the needed components and provide some things like scripting support, resource management, and initialize a graphics system (maybe Ogre3D?). The rest of the application should consist of components. One for graphics, one for physics, one for application logic, etc. They should not depend on each other, so each one can be reused for next games and the pieces for the application can be developed independently. It also means that old games could benefit from e.g. a newer graphics system.
Third, we should create tools to easily create content. Most of us aren't familiar with tools like Blender (which IS a great piece of software), but do have ideas for a cool new character, car, or an environment they'd like to see come to life. Because of this, we should create tools to easily create different kinds of content, the way that the MakeHuman project does and integrate it with the aforementioned simulation engine and website.
Also, there are a lot of objects that can be described. A car for example - once you have an idea of what a car is - can be described with a number of parameters. A car has a base with ... space between the wheels. Its roof is ... high and the corners are (not) round. It has ... windows and ... color. Same goes for foliage. Can't this be translated to some sort of script, with a base model and some parameters which the user can edit in a GUI? Maybe constructive solid geometry (http://en.wikipedia.org/wiki/Constructive_solid_geometry) could help here? One additional advantage of this technique would be that the resulting meshes could be as low-res or high-res as you want them to be.
The bottom line is that there are a lot of tools available to create good games. We just need to combine them in a way so that there's no need to reinvent the wheel for every project and the barrier to game development is significantly lowered so the creative minds among us can do their thing.
Of course, I'm willing to help set this up, but I can't do it alone. So, who of you think this is a good idea and would like to help set this up?