Well, if Gwen, Harry and MJ are going to meet Peter in High School, then that's a change from the source material, and it's a change that'll very likely happen, because I doubt that Peter pining after Liz Allen and dating Betty Brant would happen in these movies.
And who says that it's the best Spider-Man story arc? It's got a huge impact, and depicts a pivotal moment, but it's actually quite random in context, which I guess helps with believability, and it's a sad moment, a very tragic storyline. Spider-Man, for all his guilt, isn't a tragic figure. I'd say that the best Spider-Man story arcs are the ones that are light-hearted and fun, fully representative of the main character. No doubt that Gwen's death was important, and one of the better ones, but the best? I don't agree with that.
And I thought people didn't like Peter Parker crying or stories "about a girl".