Underappreciated by most. It expands on the previous one while playing it safe with the infamous "Superhero Third Act"

Rating: 8/10 (22 February 2020)

MILD MILD SPOILERS -- for those who want to know what to expect from the movie but don't want to be spoiled of everything, this is my review.
Iron Man (2008) is a master piece. The cinematography is unique, the characters are memorable and the story and action are compelling... for a superhero movie. I always thought if you took away the MARVEL brand and the Iron Man IP, it could easily be the story of a genius multimillionaire weapons manufacturer that realises his products can end up in the wrong hands and that he has to watchout for shady activities in his own company.
I don't know why people despise Iron Man 2 even though it essentially maintains Tony Stark's charisma, many of the themes we saw in the first movie and a deeper story of the Stark's legacy through his father. Sure it is over the top but Iron Man has always been about over the top action scenes, villains and characters.
The first act is really amazing and well paced. In the first 30 minutes, without seeing what has been going on between the first movie and this one, we know exactly what Tony has been doing, what the different parts of the government and military think about the Iron Man concept and the set up of the villain which holds the character arc of Tony in this movie. He learns about his dad's work and how everything he did (Stark Expo, Arc reactor, etc.) and stood for wasn't always nice and for the sake of prosperity. All while having a subplot related to the still-uncontrollable science behind Tony's new heart that only adds a stressing parameter to the overall plot.
New characters are introduced to only push forward Tony's character arc. The rival comapny's manufacturer who hates him joins the main villain because he had discovered something (a new technology) that Tony at the beginning of the movie said it was out of reach for other technological or weapon manufacturers. This movie thrives in irony and it makes us doubt everything we think we know without invalidating previously established truths and that for me is a win.
The two villains are measured and characterised by Tony's two "alter egos", the genius and the philantropist multimillionaire playboy. All while each of them maintaining unique and different charismas, motivations and character designs and origins. What falls short is that both are generally "overpowered" in the sense of more versatile than they "should". I mean, the genius villain has superfast hacking abilities that we have seen in hollywood before but still makes him too versatile to be relatable or seen as a "real person". So far the Iron Man franchise has always had a sweet balance between real life concerns and characters mixed with a little sci-fi-ish advanced technology but that still worked in the context of the story and wasn't too unimaginable for the time. What remained grounded was the characters who were just real human beings and behave as such. But above all what I love is Sam Rockwell's performance enhanced by great witty lines.
The only, and I mean the only thing I didn't like that much was the final boss fight with the villain (as predicted) because it was just a big dumb CGI battle. The third act it's true that is a little weak compared to the rest of the movie but it ties everything in nicely so I guess that's good film making. Overall it never tried to be anything other than a superhero movie so I don't know why people hate it so much given more MCU and superhero movies have the same sort of finale to their movies.
IN CONCLUSION: the movie is a blast of thrilling action and dynamic character interactions filled with new well-performed characters, multimillionaire extravaganzas, military/weapon manufacturer's corporative rivalries, military secrets, parent's legacies and over the top superhero action and tropes that would give you an entertaining and round experience. Plus, you get more of Tony Stark's charisma and great side characters and subplots that expand the universe of Iron Man (which if you don't know by now is the Marvel Cinematic Universe).
DOWNSIDES: Some new characters are thrown into the mix that are not fully explained unless you have seen the rest of the MCU movies that could confuse new comers or those who haven't seen the rest of them. Also they are easter eggs to the IronMan comic books and Marvel Comics characters that not everyone would pick up.
Another downside is, as aforementioned, the third act basically unravels like every other superhero mystery movie, the bad guy turns out to be behind it all and there's a big CGI battle. Basic Superhero 101 that for some might be repetitive and uninspired. I just take from this movie what it did different in the genre that was the new characters and a deeper understanding of the previously introduced ones.
-- BIGGER SPOILERS HERE: Although you should have seen the Marvel movies by now --
The only thing I didn't really like or felt it was pushed was Scarlet Johansson's character. Maybe it's because I know what character she portrays in the future of the MCU movies and know her real identity so seeing how she behaves in this movie makes no sense. But here she is used as a sex object/sexy assistant trying to seduce Tony Stark that really doesn't quite fit in the overall story. We are 100% sure Tony likes/loves Pepper as it is shown in this movie and hasn't really shown any reason he has a "cheating" past so if he ended up cheating it would be considered to be "out of character". One thing is to be a playboy and sleep with a lot of women and the other is cheating while in a stable relationship so, yeah.
Also another thing that I miss from the new Iron Man movies/appearances is that there's no longer the engineering/building up iron man suits or new elements or new technology, everything is just CGI. In these first movies they didn't mind getting Tony filthy and oily while constructing new things with a rock montage that made him look badass or even creating real props and pipes that the actor could physically touch and interact with. But I guess this has to do with the overall drop of quality in the following MCU movies once it became mainstream. everything became more rushed and each movie didn't have that sweet balance between being unique movies while maintaining an overall sense of connectivity and continuity between them. But I think it is mostly due to the short production times between movies or saturated release shcedule