I started with Dune II, it was installed in my first computer (probably by my uncle; who also gave me a copy of TD latter).
My dad was hooked on TD, DooM II, and Warcraft II ATM. However he only played red alert twice, and didn't give any chances to other command and conquers, probably due to a game called starcraft (I still play it with him, but he isn't a really good player just a terran turtler that spams battlecruisers most of the time).
Anyways he won't play any newer games than starcraft (maybe with the exception of starcraft II

), since he says they're too fast/complex for him.