Pretty much any platform you would want to support (presuming OpenGL and enough system resources) is probably supported by Mono/Unity.

Sure, but that does not make it available in more platforms than Java.

In the games industry they probably overlap, but outside the games industry, Java's support is much broader.

In this case, we're talking about the games industry, and with Unity, you can target platforms/consoles that Java doesn't get to.

That, and I haven't worked on a Java project yet, that didn't really annoy me.