Online: shooters, but only very occasionally.
The online experience that did the most for me was playing NWN user modules with a party of roleplayers. This was so rare and difficult to schedule that I quit though. Still it was unique.
With most online games I nolonger see purpose of killing, getting killed and respawn all the time, but in those NWN sessions you had the feeling it mattered, that you were working towards a final conclusion.