Same here. Dune 2 is the game that made me a gamer. It's also the game I beat the most times consecutively (iirc twice per side, so 6 times), with the next closes being Westwood's Nox (which coincidentally was the game that showed me how awesome multiplayer could be).
Dune 2 is favorite Tower Defense + Tank Rush game. Last month I played Dune 2000 Ordos to Level 8 (it's quite hard, or I suck more than I did in the youth).
There's also a "Super Dune 2" somewhere on the net for more difficulty.
This brings back so many memories. I had to find some Dune 2 gameplay on youtube... Hoping some people here will enjoy it too:
http://www.youtube.com/watch?v=EiJLOjeyDxs
Being a fan of Starcraft 2, I can't believe how painful it was to have to select each unit individually... Glad the mechanics of RTSes have evolved.