Now we all know who Spiderman is. Once just a geeky nerd, then one of the greatest superheroes ever! Now after 2 Spiderman series, Marvel/Sony want to replace Spiderman for a much younger actor. Now don't get me wrong, I can see why, but theres also a lot of reasons Andrew Garfield should stay.
Number 1. Less Work
Lets start this off with a big one. If Marvel/Sony just keep Andrew Garfield, there would be less work to be done. He's already had two movies, his origin story is already done, and he was just about to have his own big universe with the sinister six! And rebooting it (AGAIN) would be too much work, and it would be much easier just to leave Spiderman as Andrew Garfield and have him cross over into the Avengers.
Number 2. Comic accuracy
Now lets take a look at the graphic novel of Spiderman!
Ok and now Andrew Garfield!
Pretty similar right? And appearances aside, TASM Movies are pretty accurate to the latest comics (Besides Green Goblin), and the whole parents disappearing + Biological Spider cure is accurate to the latest comics.
Number 3. Fans
Theres a good handful of people that want Andrew Garfield to continue as Spiderman, and have been starting their own #BringAndrewBack or something along the lines of that. Now there is plenty of people who wouldn't mind him passing on the suit to another, but there is also a good chunk who would be upset. But this is just one of the minor points on why.
Number 5. The role
Now don't get me wrong, there are others who could put on the suit and do an ok job. But not like Andrew Garfield. Andrew does the role perfectly. The action, the drama, the great responsibility to put on the suit every day. You can feel all of that. You can feel the emotion of his relationship between Emma Stone and him (And don't tell me you didn't feel emotion when Gwen Stacy died). All Im saying is that he looks the part, acts the part, and its just, AMAZING!