The Minecraft comparison is a good one. There is a world with purpose: to survive and ultimately control nature. It perfectly indulges our most primal instincts.
In contrast, everyone is a god in Second Life and the world is empty. For some reason, this ultimate power is used to recreate the most mundane and tasteless aspects of reality:
- Consumerism -- SL citizens love buying clothes, furniture and other useless junk even when they can create anything themselves.
- Lame commercial "theme parks" like McDonalds Island etc. Even the ones that should be interesting, like NASA, fail to either educate or entertain since the medium of static 3D models is generally terrible at both.
- And of course, vice: kinky sex, gambling, pyramid schemes, and spam. These things made up most of the metaverse, last time I was in it.
By far, the most interesting thing about SL was the elaborate and imaginative attacks on the world e.g. self-replicating objects, and the equally elaborate countermeasures used to fight back.
I guess the lesson is that a virtual world needs to find a balance between innate meaning and open ended creativity. SL is one extreme, the other being MMOs that involve too much carrot-chasing to interest most people.