43.
Not counting early text MUDs, I started out with Everquest 1. I wasn't much interested in it, then one of my mom's ex husbands picked it up and had me play around with it a bit so I could explain it to him. I wound up hooked right away.
I met my ex girlfriend through Everquest and moved out to California to live with her. While there, I got into the CoH open beta. I happened to see that applications for this new game were up and decided to sign up on a whim. It looked amusing, but not like something I'd pay a monthly fee for. Hooked big time.
Over the years, I've spent time here and there in:
WoW
EQ2
SWTOR
Rift
Shadowbane
Horizons ( Good god, there was a game that could have been great but was released in an alpha condition... )
The Secret World ( Decent game, SEVERE performance issues. Graphics were not optimized anywhere near well enough. )