For comics that currently exist, as of now I'd say my old (abandoned) comic, WYIHN!, is longer than the project I'm working on right now, TGtaHR. It only lasted to chapter 3, but the chapters were about 50 or so pages long, while this one has had 36 page chapters with the same amount of chapters so far. Although TGtaHR will be longer overall, and is separated into two parts despite there being chapters.
As far as projects I have waiting on the back burner, I wouldn't know if they're longer or shorter, I don't actually write. ¯_(ツ)_/¯ Actually my stories just play out in my head like animations, and I just fly by the seat of my pants as far as chapters and stuff go, jotting down the basic idea of each chapter as they come up.