At first glance, Diamond no Ace seems like any other sports anime. It has all the ingredients necessary in order to recreate the sports-anime recipe every (sports) anime fan is already aware of. A loud and overconfident protagonist, a quiet but powerful rival, a main team full of players that encapsulate certain quirks, opponents of similar nature, matches full of hype and so on. Let me tell you though, this series is so much more than that. While it certainly has all the aforementioned elements to its story and characters, it manages to stand out as one of the best (sports) anime I've ever watched, earning its rightful place at my Top 5 favorite anime of all time.

Sawamura Eijun, as a character, is very simple. We can see, from the very beginning, that he is passionate, loud, optimistic, values his friends and will stop at nothing to achieve his goals. Your typical shounen (sports) anime protagonist, I would say. However, while all of that is true, the writing of the show truly makes his character shine. During the 1st season, he gets treated like a nuisance by almost everyone on the team, nobody believes in him and all the focus is given to his rival, Furuya Satoru, the 'monster rookie' that has managed to attract all of the attention due to his raw talent as a pitcher.
Nevertheless, Sawamura keeps trying. He practices without rest for the goal of becoming the team's ace, not caring about his chances of actually becoming one. He makes mistakes but he apologizes for them, he fails many times but he tries again and again without giving up. His journey to becoming the ace is an intriguing one and will keep you interested in its entirety.

The other characters are also quite interesting. Besides Sawamura, I can't really choose which characters are my favorite because the series makes sure to give everyone something special so it's really difficult to choose between them.

Coach Kataoka is one of the best, if not the best, coach figures in any sports anime I've seen. His coaching methods are very strict but he treats all of the players fairly and with respect. He pushes everyone to their limit so that they manage to become an even better version of themselves. As a result, every member of Seido's team acknowledges him and follows his instructions. Plus, he is one of the few people on the team that actually values Sawamura so, as a big Sawamura fan, I couldn't ignore that.

Regarding the plot of the show, it isn't that extraordinary or something you haven't seen before. We have a school that wants to go to nationals. Simple stuff.

First and foremost, our main team isn't just beginning its journey as a baseball team, like in Ookiku Furikabutte for example (another amazing baseball anime series you should definitely watch). It's a well established powerhouse of a school that is well known for its strong players in all of Japan. This of course, raises the stakes even higher since all of the opponents the team faces are also powerhouse schools. Essentially, you end up having matches between baseball giants and that makes the show even more enjoyable to watch, as the hype levels can rise at an enormous level, depending on the matchup.
Another key difference is its unpredictability. Many things you wouldn't expect happen in this show. Certain decisions, injuries, wins, losses, all is possible when we're talking about Diamond no Ace. This makes you unsure of what will happen next, and while certainly, a sports anime being predictable isn't a bad thing (Kuroko no Basket is also one of my favorites of the genre), you appreciate when a show of this genre can take you by surprise sometimes.

Production I.G. together with Madhouse did everything they could to bring this to the small screen, and while animation wise, it can't be called that great a production, it's pretty decent for its length. I personally also love the music, as repetitive as it seems most of the time.
As for the voice acting, it's one of the main reasons why I adore the anime adaptation. Ryouta Oosaka gives life to the character of Sawamura in a way that I appreciate to no end, truly the perfect casting for the role. That goes to Takahiro Sakurai, as well, for his impersonation of Miyuki Kazuya. Those two were born to play those characters. The rest of the cast is phenomenal, too, as one may expect.

Tip: Since baseball as a sport is very famous in Japan, this series acts as if you know at least the basics of it. I would suggest you search it up a little bit before watching.