(Listed under directed promotion because, well, I'm working on a project and thinking about these option for it).
Let us say that a new game thing came out, with a community site launched to support it. A setting, premise, and so on, all online, downloadable.
This hypothetical community might...
(1)...present a whole game, with a solid (though not necessarily genius) set of core rules set up as "official", but encourage variant rules and setting bits, as variants.
(2)...present the premise, the kinds of characters, and the setting - but play down the rules, so that the "official" rules got no more real attention than any other set, and again, more creations were encouraged.
All other things being equal, which of those would make you interested in taking part? Or is there some other variation on those that would make you sit up even more?