Well he did use Cyborg as a buildup in preparation for the reboot in Flashpoint, which made sense. It seemed like it was already planned to make Cyborg as a founding status with the League around that time.
And didn't other characters in his Titans run played as much of a big role as Cyborg, though?
I do think Geoff Johns is fond of Cyborg. And is a real fan of the character. But him claiming Cyborg is his top 5 all time favorite characters, eh I'm not so sure about that. He probably said it for PR reasons lol. But I could be wrong on that of course. Geoff Johns is regarded as a top tier talent and have written a lot of characters really really well, but I don't think Cyborg is one of the best characters he's ever written imo. But then again liking a character and writing him professionally are not the same thing.