Okay - Tiberian Dawn - Set in the future, a meteor from space carrying strange crystals crashes near the Tiber river. The crystals are found to contain very valuable materials. The Brotherhood of Nod, a terrorist organization, uses Tiberium to gain power and influence. You battle it out over Africa and Europe to destroy the Brotherhood of Nod as the GDI. And if you destroy his temple with the Ion Cannon, you get a cool cutscene
Tiberian Sun - Moving along, Kane, the leader of Nod, survived the final attack on his temple on Bosnia, and is back. Using new technologies, including hybridizing humans with Tiberium to create mutant atomic supermen, Kane is bent on destroying everything and taking over the world - again. As the GDI on a larger budget this time, you get to kick his ass and finish him off.
Red Alert - Einstein decides that he was totally wrong on this whole 'time' thing and goes back and kills Hitler before his rise to power. This alters the timeline, leaving Josef Stalin free to roam across Europe. As the Allies, you get to crush the Soviet war machine.
Red Alert 2 - Even further down this corrupted timeline, the premier of Russia, hellbent on reclaiming power for Russia, is influenced by his creepy ugly sidekick Yuri, who also just happens to be psychic, as well as probably a closet pedophile. Commence blowing stuff up.
Generals - Set in the real world with real-world weapons, where you fight real nations and 'a terrorist organization' that happens to use... real weapons we were told to be scared of (SCUD missiles? F-22's? F-117-As?).
Yes, I can definitely see how Generals is a C&C game. What with the fact that C&C up till Generals was about its OWN plot and its OWN universe, now suddenly we're fighting in real situations? What did you idiots need, a mission where you stop the 9/11 hijacking? I like how I'm always the only one on the internet to ever use my brain and make the connections between these things. I also happen to be the only one who thought Starship Troopers sucked ass, and wasn't even entertaining. Coincidence?