So a fully functional physics engine, a complete procedural tree generator, a self-contained front-end system, a reasonably complete animation package, that's fine, that's great stuff.
Sixty percent of a solution plus an API is not okay.
A complete solution to a problem (no matter how niche) with the smallest integration surface is key.
If you want to know what sorts of libraries the game industry wants to license, take a look at RAD Game Tools, they are the masters of this stuff. Some of the stuff they are currently focused on are large data-set compression/decompression (Charles Bloom) and I would guess some sort of tool/library to generically handle sparse virtual texture rendering (Sean Barrett) which is similar to id's megatexture technology... though the SVT guess is more speculation on my part than public knowledge.
In any case, this market is probably not a great one to get into unless you are a deep subject matter expert in one of these areas (or you want to become one and have a lot of time to spend doing so), the bar is set pretty high already and few game development studios are willing to put any effort into exploring solutions that aren't either well-proven or from people they already know and trust (the game industry is still rather incestuous).