the original C&C was just that - original, although the concept of the strategy game was spearheaded, also by westwood studios, in the form of Dune 2
plus the cutscenes in the original C&C was a lot nicer than the following games... it was as if they just weren't trying as hard
then there were C&C RA 1 and 2... RA1 was ok, again, introduced some nice new elements and TANYA! (girly muhahahaha)
Tiberium Sun had some very sweet graphics and an ok nice storyline, with the possibility to take different storylines along the way... plus things like the mutant hijacker was born here, or the laser fence, god i loved that
Generals... generals was ok, but didn't really have any storyline to speak off - had some nice new game elements, with the hackers, the udnerground tunnels, and stuff like that
then there was C&C3... the final(?) chapter in the C&C saga - nice gameplay, although i got a bit tired of multiplayer zerg tactics with mammoth tanks.
i'd rather play Supreme Commander these days - has better music too