FreePascal is certainly viable on Mac OS X.. Have a look at these 2 threads where I posted about the stuff I did on Mac OS X using FreePascal...

http://www.idevgames.com/forum/showthread.php?t=13163

http://www.idevgames.com/forum/showthread.php?t=13138

You other alternatives are Objective C/C++ or possibly Java.

One thing to keep in mind is that the Mono ( the Free version of C# ) team, have started a project called Mono.Xna ( uses OpenGL instead of Direct3D ), which would make XNA essentially cross-platform from Xbox 360 to Mac OS X and all the other platforms that Mono runs on. So all you would need to do is code to the XNA api and just recompile for for each platform that you plan to deploy to. This also means that you could use Chrome to target all these platforms as well.