Kenneth Branagh did not receive an Oscar nomination, despite being nominated for Sag, for portraying Iago in Othello.
This version of Othello does hold two things in common with the 1965 version starring Laurence Olivier. That being both star famous Shakespearean actors, Olivier and Branagh, who usually tend to direct their own adaptations, but in this case leave it in the hands of another. One other thing in common is just like Frank Finlay in the 65 version, the award recognition for Branagh came in the supporting category even though the story follows Iago's perspective as well as he has the most dialogue, in addition to having the most influence over the story. The similarities end as the 65 version basically took on the aesthetic of a filmed play, whereas this version attempts the Zeffirelli's approach of putting it in a setting most seem to imagine it takes place in. One other major difference, which also holds true for the Orson Welles version as well, is that the "bigger" actor plays Iago rather than Othello. Although one could argue otherwise in regards to Laurence Fishburne and Kenneth Branagh in the grander scheme of things, that certainly was the case in regards to the actor's stature in regards to Shakespeare.
This makes his Sag replacement even more ridiculous though since this version seems like it perhaps gives even more focus to Iago than usual, which is really saying something. Iago is perhaps Shakespeare's second most infamous schemer, I'll be getting to the most infamous one soon, even though this version takes a bit of a similair approach that Olivier took in his depiction of that other schemer. Like in that film, this film makes it almost as though the audience itself is a co-conspirator with Iago since Branagh instead of delivering his monologue to himself or to the stars or something, he delivers them right to those watching as though he is speaking directly to us. Now because of this perhaps Branagh takes a very distinct approach in realizing the character. Roger Ebert claimed Branagh played the role as though Iago was gay and interested in Othello, and at least in his review with Gene Siskel acted as though this ruined the film. Although apparently it seems Ebert himself may have been tricked by Branagh's approach for the character, which is not as simple as that.
Branagh plays Iago as a man of many faces, and is excellent in his realization of how it is that Iago works as a manipulator. In his scenes with the hot headed Roderigo Branagh plays them as though Iago is a bit of the man's personal instigator, always just prodding him along with some negative encouragement to make some rather harsh decision which he naturally hopes will cause him to fight the prideful Cassio, which in turn Iago hopes will cause Cassio to lose position of confidence with Othello. Now with Cassio perhaps one could interpret Branagh approaches gay, though I find it is more of the over enthusiastic hanger on, as Branagh plays Iago towards Cassio as a very soft man who just seems to be wowed to be in his presence, simply encouraging any foolish action through just how how supportive he seems. Branagh does this well as in both instances there seems to be no threat of a manipulator since he basically seems to just tell Cassio and Roderigo what they want to hear, even though that all just turns to what he wants to happen.
Branagh even continues this with the two main women of the story the first being Iago's own wife Emilia. Branagh again is terrific by showing Iago just playing with her the whole time as when she tries to give him affection he treats her as though she is a bothersome bore, but when she offers any aid in his scheme Branagh changes Iago to the passionate lover as though Iago is giving her motivation in to ensure she continues to aid in his schemes. With Othello's wife Desdemona Branagh instead portrays it as Iago is just the perfect sort of best friend in for her to espouse her fears to, and the most gentle shoulder to cry on as Branagh only suggests such an honest in his interactions with her, though without a hint of hidden motives except of course when she's not looking. The most important relationship though is obviously with Othello himself. In the early scenes, before Iago has created the trouble, Branagh presents Iago as the man with the warmest of smiles whenever Othello is around, and only ever there to lend a hand of support to his commander. Of course as Iago plants the seeds of doubts in Branagh still conveys such a trusting element in Iago, as he stays calm, even in Othello's outbursts, and just seems there to offer the righteous support of a honest right hand man. Every one of these faces shown to these people though is wholly false, and the true Iago that we see is when he addresses the viewer, which are my favorite moments of Branagh's performance. Branagh is ice cold in these moments as Iago marks out each step of his plan clearly having no emotion whatsoever in regards to the suffering he is about to cause. The only strong emotion Branagh reveals is a palatable hatred in Iago towards Othello, and this devious joy Iago seems to derive from his manipulation possibly revealing what motivates him. Although I would not necessarily classify this as one of the very best Shakespearean its very strong work, and is another example of Branagh excelling in finding an effective variation of one of the Bard's most notable creations.