The Fate series is known for a lot of things: history, action, a litany of alternate endings and spinoffs. However, what's integral to the Fate formula is its inherent sense of pairing. Whether this refers to the professional relationship between Servant and Master or the romantic intentions that come with being historical fan fiction, Fate is all about A and B coming together to create emotions that no single character could accomplish.
At the center of the series' partnerships is that between Shirou Emiya and Artoria Pendragon, aka Saber. The two are partnered within Fate/stay night, Unlimited Blade Works, and Heaven's Feel but are given much more romantic intent in the former. This list will be looking at the two and deciphering whether Shirou and Saber are the perfect pair (or if they're the worst).
10 Worst: Training
A huge thing that may stick out between the two among all of the Servant and Master pairings is the massive disparity in training. Saber is a trained knight well versed in the ways of magic. Shirou Emiya is the adopted son of Kiritsugu Emiya who refused to bring up Shirou in the ways of magic after his own battles in the Holy Grail War.
While the actual game is dependent on the actual Servant, it would help of the actual Master had more magic and combat training. Throughout Fate, the young version of Shirou is practically drowning in an entire ocean of combat and magic abilities, leaving Saber to carry the weight.
9 Perfect: Honor
A key element to any good partnership is shared interests, and Shirou and Saber definitely have that. Saber is the noble knight, Artoria Pendragon, or, as she is known without the Fate change, King Arthur. Though she failed at her mission in that life, she'd carry a noble sense of duty in her new one.
Shirou has a combination of survivor's guilt and the wisdom from a changed Kiritsugu Emiya. He's always dreamed of being a Hero of Justice that would protect anyone and everyone. With two noble hearts put together, they can at least count on beating in harmony.
8 Worst: Knowledge
Something that may affect their relationship both professionally and romantically is the lack of knowledge between the two, where Shirou's upbringing once again hinders his participation. While Saber is both an experienced magus and participant in the war, Shirou has next to no knowledge of the magical world, its families, or even the legendary figures fighting in the Holy Grail Wars.
This removes some caution between the two and leaves Shirou to plenty of surprise. There's plenty to be said of bridging a cultural gap between a modern, Japanese boy and a noble English knight but not enough between a kindergartner and a professor.
7 Perfect: Destiny
While they may not know a lot about each other, do they really need to know anything at all? Shirou and Saber were brought together by a strong string of coincidences and happenstance that can only be described as, well, fate. In Fate/Zero, Saber was the partner to Shirou's adopted father Kiritsugu who used her scabbard, Avalon, to save Shirou's life.
That bridge between Masters already makes them an auspicious pair, but the fact that the series is practically screaming that Shirou is the scabbard to Saber's sword is a loud enough proclamation for their destiny.
6 Worst: Magic Ability
As explained above, Shirou lacks both proper training and education within the magus world. While this is already plenty of a handicap, things only get worse. Now, to be fair, Shirou could and technically has grown to become a powerful magus. Honing his reinforcement and projection magic, Shirou one day becomes Rin Tohsaka's Archer, a powerful Servant capable of manufacturing any weapon and more.
However, that would be his distant future self. His current self required Saber to do a lot of the fighting on her own. Though this would change in the story, the two still had to compete at a distinctive handicap.
5 Perfect: Determination
On that note, Shirou did work like crazy to make up for his team's difference in power. His resourcefulness has more than saved his own skin when he was ambushed by other Servants and Masters, and he has worked tirelessly to also protect Saber. He even has Saber train him in a hardy, meticulous process right in the middle of the actual war.
Saber on her own was determined to protect Shirou, help him, and do what she believed was right in the midst of battle. When that would eventually have its wear on Saber, Shirou would even go the extra mile and sacrifice his own magic circuits just so that Saber could heal. While this meant weakening himself as a magus even more, he didn't let that distract him from what he was protecting in the first place.
4 Worst: Too Many Heroes
As addressed above, Shirou has always aspired to be a Hero of Justice who would defend anyone and everyone. For awhile, this meant trying to protect Saber, someone who was much stronger than him, from fighting other Servants and Masters, people and practical monsters who were also much stronger than him.
While this is a noble gesture, Saber doesn't actually need that much protecting and, in turn, had to work even harder to protect him. This would change towards the end of Unlimited Blade Works; but for a good portion of the series, they weren't even a team, just two people constantly pushing each other out of danger.
3 Perfect: Shirou's Compassion
While that sense of regard for each other may be seen as unnecessary for the Holy Grail War, it certainly reinforces a stronger bond between the two. For many of the Holy Grail War participants, the Servants are not seen much more than actual servants, people meant to service the needs of their Master.
However, Shirou doesn't feel this disparity between him and Saber. When he sees her in danger, he doesn't see a Servant or even a partner. He just sees another person and tries to protect them regardless of their abilities or the danger. It's a sense of compassion that helps make the two more than a regular partnership and one of the best pairs in the series.
2 Worst: Other Love Interests
While having multiple love interests is practically half of the interest in the Fate series, it doesn't create that many ideal opportunities for a strong partnership, professional, romantic, or otherwise. Depending on the route, Shirou could end up with Rin Tohsaka or Sakura Matou, but Saber herself is still left with feelings for him.
While this creates fun narrative tension for the audience, it's not an ideal feeling for two professionals just trying to survive or two lovers trying to make it work. Love triangles and harems may be an anime staple, but they're not necessarily healthy.
1 Perfect: Love
With that being said, there is something between the two of them. As stated earlier, the relationship between Shirou and Saber is the only consistent one between the routes, even though Shirou himself may end up with someone else. In the ideal setting, i.e. Fate/stay night, this meant that their bond was stronger from the rest.
This close relationship was a key part of the two being able to exchange mana to save Saber later in the story. While it may not always be the ending love story, they are the series' core one.