Pete, what didn't you like about the film to not rate it highly? High Noon has always been considered controversial in its content, music and cinematography. As I mentioned, the director and screenwriter meant it as commentary on the hearings of the House Committee on Un-American Activities going on at the time. Dimitri Tiomkin's musical score, as you said, helped in creating the tension which rose during the film. Floyd Crosby shot the film in black and white without the use of filters in an attempt to recreate the photographic style of the 19th Century. And Gary Cooper played the role of Will Kane in the Method Acting style taught by Lee Strasberg. It was one of his finest performances of his career.
One of the things I don't like about the film is the relationship between Kane and his new wife. It would have been a lot more believable if he married someone his own age, rather than a gorgeous young woman getting hitched to a miserable old man! And his ex girlfriend is another gorgeous young woman (who was previously with his rival but is now with his deputy!!).
Plus the fact that this young Quaker woman with strong religious views seems happy to get married to someone who doesn't seem to share her beliefs and has obviously been around the block a few times.
There never seems to be any spark between them as a couple. That whole relationship just never clicks for me, yet it is a major factor in the film's plot.
Another thing I wasn't keen on was the fact that all this tension builds during the film, but then the final shoot-out ends up as a bit of an anti-climax.
It's a great film in many ways and I know it was ground-breaking for it's time, but for me it isn't a real classic.