I remember RO. It used to be the best back in the day, everyone use to play! I played from the Open Beta on Sakray. I only had a level 70 Priest and Wizard, but even that was still alright. Nowadays, its a bit lackluster compared to other Korean MMOs.
I prefer Runescape seeing as most of my friends in real life go on there too and the graphics and gaming isn't too 'hard-core' , I used to Play Habbo but well i got bored recently.