What qualities define a good rp?

[Rein Isa Sote Eluryh]

I am working on creating an rp that will draw people into it and not let go. I'm tired of watching people join rps then disappear just as quickly when their fickle minds move to the next big thing which they won't spend more than five days and three posts in before they vanish from it as well. I guess this happens for the same reason that people join guilds just to be inactive. So, I want to know what kinds of characteristics people want to see in an rp that will keep them hooked till its conclusion. Please share your rping desires with me.  

[CrystalGemIz]

Well for one thing it depends on Genre. Also Literacy. It is very important.