Aw, I loved that version of Peter. The lesson he learned at the end was exactly what Ben told him: when you have the power to help, it's your moral obligation to do so. He still has a lot to learn about responsibility and recklessness, though, which I consider a good thing considering where his arc is going. Peter's lesson in responsibility shouldn't be a one-time deal, imo. He's learning and growing gradually, like an actual teenager (he was still reckless and cocky in "The Night Gwen Stacy Died" in the comics, after all, and that was after his big lesson in responsibility that made him Spider-man, too). I found him very likeable and relatable, but to each their own.
As for (unintentionally) unlikeable leads: I agree with Anakin, and I also hated that kid from Tron: Legacy.
However, I tend to admire movies that manage to pull off intentionally unlikeable main characters, like Bad Santa and Young Adult.