OK, calm down guys. You clearly have little understanding of the world of IP and patent law. I know I wish I didn't have even the knowledge I do, it is rather tedious, and seems to mainly be an excuse to keep lawyers in jobs.
This guy isn't claiming to have thought the idea up. What he has done though is buy a company which apparently submitted a patent in 1995, which has never been acted on.
Now, the salient points for the defence will be:
1. Was the patent application valid in the first place? The lawyers will pick it apart, and any minor details that are wrong can render it invalid.
2. Prior Art- does, for instance, the work of William Gibson count as prior art? This is far from clear cut.
3. Prior art- were there any 3D virtual worlds around before the date of the patent application?
4. Does "but in 3D!" count as a real "innovative step" over a 2D virtual world, or can it be argued that it was an inevitable direction the technology would proceed in?
Many, many approved patents are in fact junk. Often, the only way to find this out is in fact for someone to infringe one, and for the patent holder (who may not be the original inventor- after all, if I invent something at work, my employer gets all the rights) to try and sue for infringement.
Clearly, the previous owner of these rights never felt it worth pursuing. Perhaps there's a clue there.