This is very much in Stan Lee style. He's not going to publicly bash a film before it comes out, but the guy knows crap when he sees it.
Remember that old Spider-man TV show? At the time it came out, I remember a magazine article where Stan talked about how he was very excited for it, and that finally fans would get a chance to see a live action Spider-man.
Fast forward 20 years, and in the mid to late 1990's Stan appeared on the old Dennis Miller show, when a Spider-man movie was still in development hell. Dennis asked Stan when they were ever going to make the movie. He then said as a passing joke, "well there's always the old TV show", to which Stan replied, "Don't watch that. That show was terrible! That show had none of the elements of what made Spider-man great."
All this to say that Stan's not going to bash a film before it comes out.