You have tested Google Earth, Second Life and maybe Metaverse, but you have probably never heard of Geosim Philadelphia. I've tested a bunch of virtual worlds and all are certainly interesting, but Geosim Philly beta, which just launched 2 days ago was the first virtual world that got me engaged.
Geosim created an amazing virtual world (in Philly) that is qualitywise far better than what I've ever seen before. The best part is that the virtual world is actually the rendered real world (so far only Philly).
And better: There are no strange islands like in Second Life, no flat cars as you've seen in MS Virtual 3D, no black walls and people like you've seen in Google Earth.
After having seen the demo and having installed the client I finally see what the power of virtual worlds are. We are just at the beginning of an incredible interesting industry.
Not sure why, but I feel like someone took my Atari (=Second Life) away and hooked me up with a 6 GHz (=Geosim) machine. Whoever counted Virtual Worlds out just doesn't understand what's possible with high-def 3-d worlds. Telling your kids that you used a search engine without a graphical interface will probably make you smile the same way that you smiled at your parents, who climbed on the ladder in the university library.