They shouldn't of used the symbiote in this movie,they should of held off on it to give Tobey something to look forward for later.They should of just made S-M3 Harry as the main villain,and they should of thrown in some other villain.
^Yeah it wouldn't of been anything amazing in the visual department,but the story would of been juicy.Plus it would of had more than one villain,so it would of topped part 2.
Then in part 4 they could of used the symbiote for spidey that he uses to fight Lizard and Kraven.Then in this movie,the visuals would be amazing with the Lizard.
Then you have part 5 with Venom,and Sandman.Where the visuals would of doubled since part 4.Plus Venom could of been in the movie right from the beginning.
And part 6 would be the sinister Six.And the visuals would of topped part 5.
That's how it should of been done,by making each one a little better than the one before it.Now were finding out what happens when you put all of your eggs in one basket.