Yeah, for the film to be successful, the whole original cast would have to star in it. If BATMAN hadn't trampled GB II, GB II could've hit it as big as the first.
In my book, GB is a concept so fascinating, so fun, so action-packed, that no particular people were required. Just the same characters. I mean, they have high-tech, cool, kick-ass weapons to fight Ghosts with. Not nets or incantations. Whereas other “Ghost-catching” movies were rather lame, and the “ghost-hunters” in them were pretty damn lame, Ghostbusters' main characters could be heroes and just kick ass.
That's why EGB hit home with so many people. Because the concept of GB is what sells it to a lot of people.
Bill is not required to make me happy. As a matter of fact, NO GBIII at all would please me. Because they're all wayyyyy too old. I wouldn't be happy with it no matter who all was in it. I'd rather see them come back for a TV thing, or just give the rights for their images to be used on all merchandise.