I'm sorry, but I could not help to offer my opinion.
For a project intended for distribution, us UNIX kids (that includes OS X) would prefer that you do not use C#, though many (most?) of us do have mono installed. Also, many users do not have java installed. I personally install it whenever a university course requires it, and uninstall it immediately after.
If this is purely for hobby, try every language mentioned. One will click with you. Besides, each language you learn will broaden the way you think about accomplishing a task, making you a better overall programmer. If you're competent in GML you should be able to pick up most any language pretty quick, assuming you're determined.

My current game project has an engine in C++, with bindings for lua scripts, and I love it.</whocares>

Gil is very right in recommending SDL. Cross platform, flexible, (relatively) simple, good.