You were certainly an unfunny choice for this movie. But with a motley cast, a motley crew, and a motley group of characters out to save the world, why not hire the cinematographer from Easy Rider and_ Five Easy Pieces?_
Both you and director Ivan Reitman have talked about how comedies typically have a look--and how this movie should not have that look. Instead of a simplistic comedy approach with high-key shots and bright colors, _Ghostbusters _is shot like a serious film. You added a distinct color cast, but otherwise let the scene define the tone (rather than imposing yourself on it). There are sequences that look like drama, documentary newcasts, and epic adventure (that 2.35:1 anamorphic aspect ratio!). This allows you to set real stakes in a plot that is patently ridiculous. It also allows for a very broad range of humor: from pun-tastic setpieces and light improv to dark sarcasm and tragic irony--all within the same film.
Through a consistently (and I imagine painstakingly) unobtrusive filmmaking approach, you allowed the movie to conjure it's own reality. By making a comedy that didn't look like a comedy, you made people believe this unbelievable story. I think that's a key reason it's stood up so well - and even improved - over all these years.