Tom Hiddleston did not receive an Oscar nomination for portraying Loki in Thor.
Now I say Thor is an average superhero film, because it is. Not every character works, the romance doesn't work, and Kenneth Branagh does not handle the action scenes in an especially compelling fashion. However the film is worth noting for its specific achievements for the Marvel cinematic universe. One being that it successfully bridged the far more mythical elements of the comics universe to the technically more grounded aspects set up in Iron Man. The other thing the film brought was the good Marvel villain or at least apparently the only villain people seem to ever remember with Marvel. Now Tom Hiddleston has had more chances with the character but it is interesting to see actually how Loki changed in terms of his role per film. In the Avengers he was a straight forward villain, though entertainingly so, and later in Thor: The Dark World he was basically a rock star anti-hero.
Hiddleston began here with Loki at his most low key (no pun intended). Now this is rather fitting given that this is before any idea of Loki's villainy is known to the central characters, playing the sly manipulator rather than the grandiose super villain. Now Hiddleston deserves a great deal of credit, along with Anthony Hopkins as Odin, for effectively grounding the whole Norse elements of the story. Hiddleston importantly does not show his cards, and actually plays the role as though one never heard of Loki before in comics or mythology. Hiddleston rather effectively instead portrays Loki very much as the calm thinker of Thor's group, and the more reasonable of the two brothers. Hiddleston succeeds in making the whole early manipulations of Loki, to set Thor up to be expelled, wholly believable. Hiddleston does not emphasis a slick charm, something he would do in his later turns, but rather exudes a sympathetic support.
Loki's plans of course work early on, which gets Thor sent to Earth, but in doing so Loki finds he was in fact adopted by Odin from the gods' sworn enemies the Frost Giants. Hiddleston brings a surprising degree of pathos in his moment when confronting Odin over this. There is no simplification in his portrayal as he reveals Loki somewhat lost with understanding over his exact purpose. Hiddleston does not suddenly make Loki's nature change, and importantly brings the history of Loki and Odin to the scene. When Odin collapses, Hiddleston voices genuine concern in Loki for his father, bringing to life a very real connection that should be prevalent between father and son. It seems like this might change though as Loki assumes the throne of Asgard, and attempts to ensure that his brother never makes it out of Earth.
Hiddleston in these scenes brings more of the Avengers Loki, though still a bit more subtle, in revealing the cold villain who seems to be trying to usurp all power for himself. Hiddleston though plays the villain well and does so rather bluntly particularly when he goes about making a deal with the frost giants for them to murder his father. This is not Hiddleston compromising the rest of his performance though. The reason Hiddleston is playing the pure villain is because Loki himself is playing the part of the villain. Loki ends up betraying the frost giants by killing them when they try to kill Odin. In the end Loki's plan is only to prove his worth to his father, and Hiddleston's work matches this intention so well. There is a real desperation in the act, and he's actually surprisingly moving in the end as he reveals Loki's sadness as he fails in this task. Hiddleston never loses the personal connection in his work and he makes Loki's defeat in the end surprisingly tragic. It's a strong performance by crafting a compelling villain who never is defined by his status as the antagonist.