Good RP's rely more on the players and not on the admins. The admins are there to ensure the players follow the rules to a good rp, but t he players have to execute it correctly. Most of the more "quality" rps end up with a group of 5-6 people rping on their own while everyone else is stuck trying to ring things up with other players.
A good rp could, theoretically, be achieved with 1) good ringleaders or people (usually admins or moderators) who know how to rp and can keep a group of people in line. You want everyone to participate, so you want someone who can keep that going.
2) It always needs a decent preset build, letting people build their own bases at will is a horrible idea, not only does it add more on the to-do list of admins, but it can mess with the overall feel. If your default build is crap, no one can enjoy the play.
3) A storyline, something people can follow. No, this does not mean the admin makes up the story and has to be their every second of the way. Just so people don't get off on the wrong foot or end up doing something completely unrelated and stupid. This goes hand-in-hand with random events that effect most or all of the rp, causing large or minor changes, but always at the right time and never unfairly.
4) Community, you can't run a rp server with people that don't know what they're doing. Sadly, this means you will have to kick or ban some people who are doing it wrong, even if they aren't meaning to do anything bad. But you need active people who know what they're doing to keep the rp running smoothly.
5) Size, this all depends on how you want your rp. If you want to keep something simple with a set storyline that you create, limit the size to a smaller amount. If you want a mostly free roam, hell, go as large as you want. The more people you have, the more VARIETY you have in the rp. I can't have a band of outlaws and a whole town of goody folk with only 5 guys, if I had 20 that would mean both sides would be massively developed.
6) Some way to keep people informed of everything and constant updates to the rp and build itself. Things could happen when 2 rpers are absent and they comeback, not knowing what happened, rping about something that doesn't exist anymore. A newsboard, a newspaper, anyway you want to do it, just do it, its helps players a ton. And with constant events and an evolving rp, you need to keep your build changing. Maybe a ship crashed, maybe the town got blown up, maybe there is a site of death somewhere. It should all be updated constantly, not only does it look pretty, it gives players a new thing to expect everytime they come back to play.
All of above was just me spouting stuff, I could be wrong in some points but I think most of it is pretty good :I
