Those cutscenes really helped with the immersion! I think those really gave life to the story, while providing a sense of progression through the game.
Even as a kid I found them quite cheap, but they still had some kind of charm and an instantly recognizable style, with those huge logos clearly classifying you as good/evil and the white noise at the end.
As I finished the GDI campaign and inserted CD2 in the player I really felt like I was giving up to the Dark Side of the Force or something 😛