Sports anime has traditionally never been my favorite category because aside from a few exceptions, it's always a one man show of how an extremely talented person manages to conquer all obstacles to become the best in the sports.
Fortunately, Giant Killing IS among those few exception.
I'm not a big fan of soccer nor sports animes in general, so before I even started watching it, I already tagged this anime as "watch one and throw away" because there was nothing in the description of this anime sounds interesting, at least to me. But one episode is all it took to change my mind on that. Maybe it has something to do with the ongoing FIFA World Cup at the time, but Giant Killing really is a sports anime of a different kind for many reasons. For one, even though there are some character centric development throughout the story, it's never been just about one person. On top of that, the story introduced a crucial element of team sports that most other sports animes usually ignore: coaching. This added a dimension known as strategy into the a story that normally would be dominated by only hardcore action and one man's determination. And that is what made this story so interesting.
Although the story itself is far from over, the anime ended at a point that everybody could be happy about. They could easily extend this series into another season but that really wouldn't be necessary. So in short, I think it ended on a good note.
Final scoreboard:
Drama: 90 (Sports drama)
Comedy: 86 (Not its focus, but fun for what it has)
Action: 90 (Soccer action)
Art/Animation: 86 (Interesting style)
Sound/Music: 84 (Adds to the excitements)
Character: 92 (Very well developed)
Plot: 83 (semi-formula, but still interesting)
Ending: 88 (Well enough)
Re-watch value: 70 (Loses some excitement, but still fun)
Overall: 88 - Best sports anime I've see lately
Recommendation: I've read someone's review saying Giant Killing is GTO trying to reform a soccer team. I think that has much merit to it. So if you like GTO type story, and don't mind sports anime or soccer, you definitely don't want to miss this. Or if you just like sports animes in general, this is probably one of the best sports anime I've seen in last couple of years.