I read a reaction awhile ago that I agreed with. It seemed like Sam Raimi wanted to make a movie about Sandman while the company wanted a Venom movie. That kinda explains why Sandmans character is well developed and Venom seems tacked on.
The first time I saw it was watching the DVD with my roommate. Both of us loved the first two and were worried about the bad reactions we heard for three. Throughout the entire movie we kept looking at each other and exclaiming either "What the ****?" or "Jesus this is terrible." The way they tried to show Peters character development seemed like a terrible parody.
Also, might I remind you:
All in all I think it's the most disappointing movie I have ever seen in my life.