I liked RuneScape a lot back around 2005 - 2007. As far as I remember the appeal was:
- the sense of community. You'd meet a lot of bizarre people in the game, especially if you played during weekdays when all the normal, non-retarded people were at work. Making new friends from faraway countries was still a novelty to me back then.
- the sense of investing in a project, so to speak. Cutting down trees is boring, but it's less boring when you know that each tree is adding to your lifetime stats which you'll keep forever.
- the fun of being part of a game that's constantly updated and given refinements and new content. This is the norm today with patches and DLC and shit, but it was cool back then to have entire new areas and questlines suddenly added into the game.
- and, on top of all that, RuneScape had some pretty decent content in terms of quests and shit, so all this is held together by a game that's worth playing (although perhaps not worth playing for two years straight like I did).
- another point that RS has was that it could be played in any browser that supported java, meaning you could play it at work, school, in libraries, etc
The genre is kind of a relic these days, I think. It was a way to blend (early) social media and gaming, but there's no novelty in walking around as an avatar of yourself and meeting other people that way nowadays, since social media is so forced upon us that you'd get more interactions and meet more people by just opening any of the big tech sites. At best, the only advantage an MMO has now is that everyone's there to do the same thing (play the game), which means you've all got something to talk about, at least.