Sam isn't the problem (even though he kind of is). The problem is that it's not actually Marvel. They've done extremely well for themselves since taking the movies back in house. But they don't own the movie rights to Spiderman, so they can't do anything with it except slap their name on whatever the studio comes up with.
None of the Spiderman movies were good movies. Frankly, none of them were even good COMIC movies (which is measured on a different scale than regular movies).
Hulk was decent. Iron Man was really good. TDK, though not Marvel, was fucking incredible. These are the movies that have set the bar. No sequel to a crappily executed franchise is going to come anywhere CLOSE to the bar. But it's way too soon for a reboot (frankly I'm astonished that Hulk managed to be as good as it was, considering the previous abortion of a film). What Marvel needs to do is buy the rights back, drop the franchise entirely for 3-4 years, and then reboot it, and do it RIGHT. No more of this sniveling, whiney bullshit. And for the love of god, cast a starring female who can ACT.