They are almost all great even Renegade although it has visually aged really fucking badly, also C&C4 is the only one I would stay away from because it's shit not even as a C&C game but as a game. Best in my books are Red 2,Yuri's Revenge and Generals, Zero Hour, those are also the ones with best mods and custom maps and there are a lot of them.
C&C Tib Dawn with it's expnsions and Tib Sun, Firestorm are free to download so is C&C Red and expansions if I'm not mistaken. C&C Tib wars, Kane's Wrath are both fun although multy has kinda died. Red 3, Uprising are both good and I'd say that Uprisng has some of the most interseting missions in the series not the most mind you, also Red 3 multy is not that good, I have a wierd feelnig that EA wanted it to be next Starcraft but it is unbalanced mess were the only viable strategy is rushing.
C&C Tib Dawn with it's expnsions and Tib Sun, Firestorm are free to download so is C&C Red and expansions if I'm not mistaken. C&C Tib wars, Kane's Wrath are both fun although multy has kinda died. Red 3, Uprising are both good and I'd say that Uprisng has some of the most interseting missions in the series not the most mind you, also Red 3 multy is not that good, I have a wierd feelnig that EA wanted it to be next Starcraft but it is unbalanced mess were the only viable strategy is rushing.