Oldest one would be Final Fantasy 7.
I borrowed my kid brothers' Ps1 just to see what games there were to play, never had a console since the Videopac 2000. It came with Wipeout and FF7 and 8. I was done with Wipeout within an hour and then started up FF7, not knowing what to expect...
100+ hours later i woke up, so to say.
Then, World of Warcraft.
Introduced to me and a friend by a friend. Never really had a notion of this online crap. Tried levelling a bit and ended up ruining the better part of my life ;p.
Comes in Far Cry 3.
Having played Wolf3d in the nineties, followed up by a bit of Doom, to me Fps's were generic, boring, same shit different day kind of games. I guess they still are. Far Cry 3 however I platinumed and very much enjoyed its' gameplay. I will probably enjoy the next Fps as much in a year or ten.