Ragnarok online, runescape, and the original Phantasy Star Online on Dreamcast.
Those things are like crack, stay away, far far away. I played PSO everynight for 5-8 hours for like a year when I was 14 or 15. I had a few characters at max levels.
You can find me on facebook as Markus Van Rijn, if you friend me just mention you're from VGchartz and who you are here.