I say this from a film making point of view only. The only one weakness I would give this movie is maybe the plot was too predictable between Tony and Obadiah, but when you look at directing, cast, cinematography, VFX, sound, score, Character-Driven purpose arc. I think Iron Man 1 is the best MCU movie just from a art pov.
It also has a 3rd arc that is mostly neat, without any of the bombastic cgi galore that came with the sequels or we got to see with Avengers. I used to think it was Winter Solider that was their best film, but winter solider was already a bit disney-doned , the cinematography of the movie sucks and the last arc with the helicarriers was over the top but I think winter solider will still be a top 3 because it is not as corny as the other MCU movies.
However Iron Man 1 is a true Jon Favreau work. It's a movie that has more in common with Star Wars Mandalorian than other MCU movies. This is a movie that was very well made and planned out and if I was a film maker, I would want to have done this movie than any other MCU movie.
I will leave with one of the best scenes of the film. This movie meant business not the comedy cartoon looking stuff we have now. This is actually what a gritty high stake scene can be without blood or gore.
Jon Favreau does not get credit enough and its a darm shame that people got too carried away with the cinematic universe thing and have glossed over this film to favours other nonsensical films like Infinity Wars that does not even have 1/10th of the film making chops of Iron Man 1