Currently playing:Kapi-Regnum (4 years)
Core Exiles (3 years)
Simunomics
Astro-Galaxy
Chosen Space..less than a year each of those.
I have also played on the browsers:
Lacuna Expanse (twice)
Capitalism Online(twice, the Ratjoy version)
Tycoon Online
Lagoon B
Transportation Tycoon
Medieval Europe (early days)
Western Somethingorother- a wild west shoot-em-up.
Some Hacker game that was played in rounds
I also like/liked Civ (all of them, even V), Silent Service, Railroads I II and III, Alpha Centauri, Master of Orion, Capitalism (the first one only) Pirates, Port Royale and Transport Tycoon(in the box.)
Oh, and Pong. Don't forget Pong.