I shall not be making a particularly formal review, though I would like to address specific key points from the series.
On the Story: As a person who watched the prequel, Fate/Zero, before this series, I will do my best to keep my opitions unbiased to the best of my ability. The plot of Fate/Stay Night is slow, confusing, and very disjointed. An important character is met once early on in the series, then does not appear again nor is even mentioned until the very last few episodes. The plot is very sexist, as the main character Shiro, as well as many other male characters, refers to women as needing protection or telling them off when they "do things girls shouldn't do", like fight battles, or act certain ways.
Animation: The animation generally is medium quality, my largest complaint being the characters emotionless and static expressions for the duration of the series. It takes away from important plot points and references to important events (and especially harms foreshadowing) when the characters express little to no emotion. During fight scenes, however, the animation greatly picks up, has fast pacing, and looks much more high quality.
Sound: I personally found the opening and endings of each season to be slightly off, paired with this anime. The music in the opening promised a world where there would be fights, but also mystery and intrigue. Then the title screens played haunting melodies...which continued into the overlay of many scenes and felt awkward. Hearing the same haunting melody of a music box during an expositional scene was distracting, and quickly became dull. The sudden changes to the humorous school life at Shiro's breakfast table and his school days was a sudden jolt in the wrong direction, in a series about a bloody war of mages.
Characters: As I mentioned briefly in my review of the story's plot, the male characters are rather sexist towards the female characters, the most serious offender being the male lead himself. As the series progresses, he amasses an obvious harem of women around him, each fufilling a single, static female role: a young child, the tsundere aggressor, the shy passive girl, the hyperactive girl, the sports girl, the emotionless girl, the sadist, the dependant, among others. Each is dependent on a male to be the stronger and allows him to dictate most of her actions, going so far as to sacrifice themselves for that man in several occasions. The only girl I saw who distinctly stood up to a male counterpart was quickly removed from the plot by said male's evil schemes, and was barely mentioned again. Her strong female role was quickly usurped by a surplus of weak female ones, all stereotypical caricatures of school life anime girls.
The men are just as guilty as the women in this case, as nearly all of the men are either one dimensional, extremely shallow, or emotionless. Notable examples include Caster's emotionless master who seems to have no true purpose, Rider's master who had no bite to match his bark, and especially Shiro. The main character, when not in "normal life" scenes, acts foolishly, has little meaning to many of his actions which he later gives little or poor explaination for (such as attempting to protect Saber so many times), is very unexpressive in his emotions (most of the time he is frowning and grunting, then suddenly acts without reason, and is generally very inept at being a developed, interesting character in the least. Many times his adopted father, Kiritsugu, is mentioned, but never is his family before the fire. He allows himself to be used by people around him, sets a blind goal without prospects of properly succeeding (and does not succeed, he instead has to alter his 'steadfast' plans many times), and does not listen to those with greater experience than he. Simply put, Shiro is a stock hero who doesn't even have any heroic qualities, aside from self-sacrifice (which doesn't work well anyway since he goes down so quickly).
Of the few good examples of characters, I will note Kojiro and Gilgamesh as interesting and dynamic characters. Each drew my interest and was exceptional in grabbing my attentions as to why they sought their goals. I will admit my bias towards Gilgamesh here, as I greatly enjoyed his character's outstanding arrogance from Fate/Zero, and I wished to see how that would translate into Fate/Stay Night. Kojiro had a meaningful purpose, a surprising backstory, and was very nobel in his actions through and through. Though not long for the screen, he was an impressive and expressive character.
Overall, I deliver a verdict of a 5/10, a higher ranking than I would like. I personally feel the series should only receive a 2-3.5, but I allowed a bias to persuade me halfway. I initially was drawn to this series after having completed Fate/Zero, and I wished to see the continuation of that grand plot. As disappointing, embarrassing, and awkward as this anime was, I was very excited and eager to see the return of Saber and Gilgamesh. The characters from the prequel to this series were of much greater depth and dimension than the characters from Stay Night, and I was very disappointed in this series altogether. I expected something, at least plot-wise, if not animation-wise, of Fate/Zero, and I was thoroughly disappointed.
I struggled through this series until episode 19, in which I only began to enjoy myself after select characters made appearences from Fate/Zero. For anyone who had not watched Fate/Zero in advance, the sudden and startling appearence of such characters and revelations about Saber and Kiritsugu (I am certain) would be odd and uncanny; why would Saber suddenly inform Shiro about having previously engaged in the Fourth Holy War? Why didn't she tell him sooner? She was very obviously aware early on, and Shiro even took her to the place where the town burned. Shiro admitted to the pain the past brought him, and Saber never batted an eyelash until her 'big reveal', which Shiro didn't even get upset about. Like most of the exposition in the series, it was emotionless and tiresome. Like Rin and Sakura's "reunion", the scene showed flashbacks that only viewers who had previously watched Fate/Zero would understand, let alone find interesting.
I am glad I watched this series in the end, though I will admit I did not enjoy it in the least until episode 19. So my advice for people interested in this series is first to watch Fate/Zero, which has far superior plot, animation, and progression. Then watch this series, Fate/Stay Night, for cameos of those characters left at the end of Zero. You will be disappointed at first, but in the end it may be worth many hours of monotonous, annoying plot.