1. It's more of a Marvel Film despite not being Disney
OK let's be honest here Marvel Studios movies are a lot lighter and comedic than DC Entairtainment and we love them for it by far the number one hero of Marvel is Spider-Man no argument so when he got a sequel in 2014 to his second reboot 2012s The Amazing Spider-Man the film was given harsh reviews but a lot of things non disney marvel get harsh reviews *coughs* Fantastic Four. Captain America The Winter Soilder was pretty dark a bit too dark from the usual Marvel routine not that it wasn't good but Amazing Spider-Man 2 had Electro Rihno and Green Goblin all in one movie what did Cap 2 Have other than Winter Soilder Nothing great that's what.
2. The Peter-Gwen Chemistry
Say what you want about The Amazing Spiderman 2 the romance was to sheer perfection probably due to the fact Andrew Garfield and Emma Stone are a real life couple. Captain America portrayed by Chris Evans is no doubt an attractive man and Scarlet Johansson is one of the most beautiful woman in the world but rather than focus on the romance and mix it up a notch they focused more on using her as a sort of Megan Fox transformers character rather than having the two share passionate onscreen time.
3.It was setting up a cinematic universe
Amazing Spiderman 2 had so much pressure on it's shoulders after all Sony owned ONE just one Marvel characters film rights so the idea of them using just Spiderman for a cinematic universe meant they were going to push further character development into underrated characters heck there was even talk about an Aunt May solo movie true it's odd and probably not SMASH the box office but a great movie is not determined by the box office.