While I can respect the writers starting off the character of Thor as a tantrum-throwing man child, all the explanation that is given for his change into a selfless hero comes from a girl he knew for as little as a week.
A week is plenty
of time in a movie, especially when Thor had such a change in circumstances.
A love story in a movie should not be based on how long it is in movie time, but on how convincingly the two characters relate to each other. You obviously found their relationship unconvincing, but it would have still been unconvincing for you if they spent a year together.
While I don’t expect much from superhero movies with regards to romance subplots, this was amazingly badly executed (and took up a chunk of the movie) – F.Y.I guys, a “crazy, homeless guy” who calls himself a god of lightning and is much bigger than and is physically intimidating to you, kissing you on the hand would not be charming; it would be change-of-pants terrifying.
I see what you mean. On the other hand, having it be "charming" instead could be intentional humor, since it subverts expectations.
The entire earth supporting cast (the scientists) were completely superfluous to the plot, as in fact were most of the Asgard supporting cast (excluding Loki, Odin and Heimdall).
So excluding all the major supporting characters, the supporting characters were superfluous to the plot? Seems a bit like nitpicking to me.
Another characterisation failure is that at one point during the movie Odin, the all-father, the ruler of Asgard, was about to hand over an entire realm of existence to what was, at the time, a destructive dumb brute. There is not even a reason for this plot-induced stupidity – it simply is.
Monarchies are stupid; just look to real life for some examples of why they are stupid.
The character of Loki was also done exceedingly well, until he is derailed in the third act to make him a more viable villain (at around the same time Thors character was similarly derailed to make him a viable hero).
IIRC, wasn't he made more
sympathetic when he revealed that his entire plan was to just use the bridge to kill all the frost giants and make his father proud?
Though this in and of itself created problems in that Loki seemed as though he would have made (and did, at one point, make) a better ruler then Thor, and I was cheering for him for most of the movie.
That's one of the movie's points; at the beginning, Loki would have made a better ruler than Thor. That's not because Loki is great, so much as Thor is not. Loki is clearly established as a manipulative liar who is willing to break the rules to get what he wants; while that's better than the brute Thor started out as, it's certainly not desirable
in a leader.