Summary:
Can I program a \"thick client\" game in C without reinventing wheels, or should I just bite the bullet and use some libr
You need to ask yourself if you are in this to build an engine or to build a game. If your purpose is to create a game, you should definitely look at an established gaming engine. For 2D game development, look at Torque Game Builder. It is a very powerful 2D gaming engine/SDK that will put you into production from day 1. They have plenty of tools that integrate with it, content packs, and you get the full source code if you want to make changes and/or learn how it works. It is also Mac OSX compatible and has Linux versions in the community.
If you are looking for something on the console side, they have that too.