I discovered it that way too. I was at uni, and alone in the house one night so whilst I was just reading various PC Mags at my desk, I decided to install a demo of a game billed as a 'superb cannon fodder' clone.One of my fondest memories of pc gaming is discovering C&C1 was like Dune 2 from a mag, and playing right through it.
This was in the age of no interwebs so magazines were the only good way of getting stuff like this. Over the next 2hrs well into 4am territory I was struggling to handle the lone Obilisk that was battering my forces until I discovered the Orca. I was hooked, and that was my first ever RTS.