Everquest. Login onto that for the first time, killing skeletons as a dwarf, the sense of danger when i wandered into a higher level area and seeing other players running around and making friends.......MIND....BLOWN! (I realise this isnt the first game to do that, i was slightly late for Ultima and others) The only games to capture some of those feelings since have been The Elder Scrolls : Skyrim (first dragon encounter was very memorable) and Shadow of the Collosus (wow) along with Dark age of camelot, best community and pvp i have ever encountered.