Honestly, I played RO because of its 2D/3D simplicity. Not only was it simple, but it had its own unique drive to it with the easy social community, the semiquesting,semigrinding concepts. and It was one of the first Instant Guild battles that was so fast paced and no matter how many people played, I never had a BIG problem with it.
(then again I think thats the reason why a lot of people played it )
I hope RO2 wont be another generic MMO with just a different theme.