I've been reading that M3G is something based on OpenGL ES...so can I work with this on iPhone OS? Did anyone do that already?
M3G is a Java API. On some devices it may be implemented on top of OpenGL ES, but that does not mean that a device having an OpenGL ES implementation is sufficient to use M3D.
The iPhone does not support Java development. There may be some thirdparty environments that cross compile Java into something that can run on the phone. I don't know of any, but I know there are tools for .NET and JS based apps. I suppose it is technically possible someone code implement something like that with support for M3D, but as far as I know no one has done it and it would be a monumental effort.
So, could M3D be made to work on iPhone, probably, but it would require getting Java working, and that would take years of developer time and I do not believe anyone has but in the effort.