Command & Conquer is one of my all-time favorite games. Tiberian Sun was a bit more 'meh' in my book - just never really finished it, but maybe I should. Command & Conquer 3, while admittedly not as good as the previous games story-wise ( not including the Scrin, at least in the way they were, would've been a huge improvement ), is certainly a good game. Kane's Wrath, though, is awesome. Kane, and by extension Joseph D. Kucan, the actor who plays Kane, is just such an intense person. I can see why millions of people would follow a leader like that.
As for Command & Conquer 4, let's just ... not talk about it. The gameplay is changed. The story is laughable. The whole thing just reeks.