He hasn't grown as a person in 2 films.
He most certainly has grown as a person over two films. I can't see how he hasn't at all.
Most pertinent example is the end of the second film, he's absolutely destroyed as a human being, but Gwen's speech showed him the importance of hope, going beyond what you suffer, ect. We saw what happened when people didn't grow beyond their suffering (Harry, Electro), they're antithesis' of Peter Parker to exemplify this growth of him as a person, he just won't back down forever, he'll keep fighting.
In the first film he started this crazy vendetta against Ben's killer, was told by the police captain that he lost traces of a hero with the selfish endevour, I don't recall Peter going after any more people in that fashion anymore, it's when he started saving instead of hunting people, that's growth, that's responsibility, that's Uncle Ben's legacy. He's actually responsible for the death of Ben Parker in this series, which I think adds more to his grief and the gravity of the lesson, I think Ben Parker was in the second film in Peter's heroic actions, in those little moments when he was helping that kid or trying to convince electro to not light his candles, I thought "show not tell" was a good thing? He's there.
He grows from a stuttery nervous teenager to a slightly less stuttery, confident teenager who graduates.
What makes Peter Parker so great is that he hurts, and he trancends that. This sums Peter up quite well, and I think the films go a pretty sufficient way in showing this.
http://comicsalliance.com/ask-chris-96-why-spider-man-is-the-best-character-ever-yes/
Don't be surprised if the next film shows Peter growing even MORE, mark Webb does his humans well, he's very good at that.
As for my least favourite line? Probably how Dr Kafka said Eletro, it bothered me deeply.
Also, to adress originalmile's qualm, Gwen said that as an indicator that they'd been on and off between films as Peter was dealing with the promise, didn't see a problem with that at all, natural line that also fills in the gaps between films, it's what you try to do.