[Spoilers for Fate/Zero and Fate/Stay Night]
One thing that people laud Fate/Zero for is its cast of predominantly adult characters. This sets it apart from most anime, which tend to have a young average age among its characters.
The more I think about it, though, the more this “strength” isn’t as good as people make it to be.
A confession: I liked none of the Masters, with the exception of Waver Velvet, who happens to be the only teenager out of them all. They all had myriad faults in them, faults that didn’t make them endearing at all–merely painful to watch. I can understand that common sense in the Nasuverse is in precious short supply, but six out of seven Masters fail at becoming decent human beings? Please.
Compare Fate/Stay Night, the VN (or anime, if you want to pick the low-hanging fruit). F/SN’s main characters are all teens, and while they aren’t as unique as the Masters in Zero were, they were more likeable. Their failings could be written off with the excuse that “they’re teenagers, so it’s expected”, or “they’re still young, they’ll know better”. I can’t be as forgiving with Zero’s Masters, because they’re supposed to be adults and I have higher expectations from them (except for Ryuunosuke, who is utterly insane). That, and I suppose that adults are too set in their ways to change for the better, so there’s little luck in that.
The most prominent example of adult failure and teenage success in Fate would be Tokiomi and Rin. Tokiomi’s justification to Kariya for giving away Sakura sounded like petty excuses, a master magus who failed at being a father and a human being. On the other hand, Rin in F/SN surpassed her father: she avoided the ignoble fate he had received, avenged his murder (a fine moment of irony, too!), and went on to enjoy more success as a magus. And Shirou was able to have his own cake and eat it, too.
Don’t get me wrong. I liked Fate/Zero, all despite the large amount of characters whom I found thoroughly unlikeable. It really makes Fate/Stay Night a more compelling work, because knowing the failures in Fate/Zero give F/SN’s plot more context and weight. It’s a testament to how good a prequel F/Z is, but I’m not proclaiming to everyone else how better off it is for having adult characters instead of teenagers.
PS: Read the VN if you haven’t. Fate/Zero enriches Fate/Stay Night in many ways.
PPS: I am going to follow my own advice.