I really wouldn't call the show silly. It was played pretty straight, and tended to deal with global issues more seriously than '60s Bond. Indeed, there was hardly any humor in the show, probably the most humorless espionage TV/Film fiction of the time (at least until the later seasons). I started watching Mission: Impossible inbetween seasons of Mad Men, because I wanted a fix for my 1960s period pieces. I was really struck by how those episodes were lessons in project management, logistics and sequential planning, and just stone-cold serious acting. Yes, the IMF themselves and their schemes stretched logic and were pretty fantastical, but it was far from campy. And I feel like the best Mission Impossible movies tend to adhere to the show's sense of stakes and tension; Cruise does his homework. Speaking of Tom Cruise, I don't always enjoy his movies, but I'm also never ever bored with his performances, either. They can't all be winners, but he clearly puts in the effort every time, and I enjoy him as an actor because of his commitment.
I wouldn't say it really dealt with "global issues," since the enemies were mostly imaginary nations, and the politics behind the missions were little more than excuses for the caper stories. M:I was really more a show about heists and con games than a show about spies; it was inspired partly by the heist movie Topkapi. But network censors of the day would never have allowed a show whose heroes were criminals, so they had to be spies so that their thefts and con games would be in the name of national security. (The pilot even had the team's expert safe-cracker suffer an accident that ruined his fingers so that he'd have to give up his life of crime.) Yup. I like to say it was more a spy procedural than a spy thriller. It reminds me of CSI -- both shows relied heavily on lengthy montages of experts wordlessly performing intricate work, with the music playing a key role in the scenes' effectiveness. (M:I was praised for its music in its early seasons, though later seasons relied much more on stock scoring.) The '88 revival series had more humor in it, probably because it was post-Airplane! and Peter Graves had come to be seen as more of a comedy actor by then. There were a number of episodes where he role-played as rather colorful, amusing characters. I think the movies have rarely felt anything like the show. The show wasn't about over-the-top action, it wasn't about the lead being accused of treason and constantly on the run from his own people, and it wasn't about a solo hero overshadowing the rest of his team. Right. He's completely dedicated to the work and throws himself into it totally, and I've always respected that dedication.
I completely forgot about the revival. Of all the IMF tech ever used, this show probably had the most unbelievable: a device where you can watch someone's dreams. I'd like to revise what I said earlier: I feel like since MI3, the movies have done a better job of sticking closer to the show, though I would agree that it's still largely focused on one lead, particularly Rogue Nation, in which Stickell and Brandt are reduced (or for Stickell since Ghost Protocol, upgraded) to expanded extras. I would say though, that the very end of Rogue Nation played out like something from the TV show Spoiler: Rogue Nation in that the Big Bad is lured into a trap that he never saw coming, and has a giant "Oh Crap" look on his face when the team reveals themselves and the scheme. The best episodes tended to be the team slipping in and out and no one the wiser. It happens a couple times in the movies (like the CIA raid), but typically not as the climax.
The revival got pretty insane at times. The tech was often even more fanciful than the original show's, and they were completely obsessed with using holograms to fake supernatural phenomena (although the original did that on occasion itself). Unfortunately, it was also frequently extremely racist. The original M:I largely avoided depicting non-Western cultures at all (except for one unfortunate episode set in Japan, where Leonard Nimoy was supposedly able to fool actual Japanese people into believing he was Japanese), but since the revival was shot in Australia, it frequently dealt with non-Western cultures, and it tended to paint them in very stereotyped and condescending ways. Also, in the later second season, the revival pretty much abandoned the whole premise of carrying out intricate plans plotted out ten moves in advance, with Jim just sending his team in undercover to try to find something out and then improvise a way of dealing with it, like any other spy show. I have this theory that maybe Phelps started to lose his edge at this point and that this was the beginning of his descent toward becoming the traitor of the first movie (although my preferred view is that the movie's Phelps is an impostor). I think Ghost Protocol was the only really M:I-like movie in the series, as I probably already said. RN wasn't very M:I-like in its plotting aside from a couple of brief bits, but I feel it did a fairly good job with the ensemble. I didn't feel Brandt and Luther were reduced in prominence, just following a parallel thread that was just as important to the whole. I would love to see an M:I movie that was just a single intricate con game in the vein of the series, more like The Sting or Ocean's Eleven than like the M:I films to date.
Which makes sense really, the new series had les time to tell their stories 45-45 minutes versus the 51 minutes of the original show. And there was always the pressure of better ratings.
You keep repeating that as if it were true, but it's not. "Being in love with a random hot nurse" is not exactly deep characterization, and it's certainly no deeper than his genuine affection for Nyah in II. Like it or not, II also solidly established Ethan as a guy who revels in the insane stuff he does, not only through his bonkers choice of a vacation activity, but through Ambrose's line about how he'll always "engage in some aerobatic insanity before harming a hair on a guard's head." Granted, that's not a lot of characterization, but what does III add to it? 'Cause I don't remember a dang thing apart from a random new love interest, whom he's been flagrantly lying to about his entire professional (and, by extension, personal) life and career ever since they met. (I don't find that very "likable" either; at least Nyah knew exactly who and what he was from the get-go.) If you want to slag on Cruise's unofficial Notorious remake for having the least similarity to the M:I TV series, that's perfectly reasonable. But I don't see the Hunt of III-RN as any deeper or more engaging a character than that of II.
What an incongruous and nonsensical thing to say about personal opinions. "Random hot nurse?" What an insulting and sexist way of describing the most human character in the entire franchise. Nyah was a one-dimensional sex object, and her courtship with Ethan consisted mainly of insanely reckless driving. Julia was written like an actual human being rather than simply a target of male gaze, and her relationship with Ethan was believable and textured and set in the real world rather than a cartoon fantasy world. The simple fact that her chronologically first scene was a dinner party with friends -- the fact that she actually had friends rather than just male love interests -- made it far more human and believable than anything in M:I-2. As I've said before, III is basically Alias: The Movie, and what characterized Alias was the way it balanced grandiose spy action with everyday, human relationships, at least in its early seasons. A ton of stuff. I'm not just talking about plot summaries, I'm talking about the details of character interaction, the texture of the performances, everything that made the characters in III feel like human beings rather than cartoon caricatures. I'm talking about how M:i:III actually lets Tom Cruise emote and show his full range as an actor. He gives a terrible performance in the first film, even though he was Oscar-nominated for Jerry Maguire in the same year, because he has no characterization to work with beyond "really pissed when his team is killed" and "sleeping with the boss's wife." He's not much better in the second film, because he has nothing of any emotional substance to play on there, just a sophomoric fantasy of seducing a sexy thief by driving really fast and then competing with another man for the control and possession of her as a trophy. But in III and GP, he has a full range of emotion to play, because it's an actual adult relationship, a marriage, with all the complexities that implies. Which is exactly what makes it more simplistic. In real life, secret agents have to deal with the question of balancing their secrets with their relationships with spouses and family. M:i:III had Ethan explore and navigate that dilemma, just as Alias did with Sydney. The fact that Julia was outside his life as a spy was a source of complication, and complication creates drama. Do I tell her and risk her safety, or lie to her and risk losing her? The brilliance of it, of course, being that Spoiler: M:i:III ending after she is taken as a hostage to get to him, she ends up being the one who defeats the bad guy and saves his life.
I would argue that the character development was only marginally deeper in M:I:III than it was in the previous films. Just because you give a character a handful of domestic details doesn't necessarily mean the audience has any more insight than they had before.
Again, though, it's not just about plot, it's about the details of performance and direction. Plot is just one facet of filmic storytelling. The characters in M:i:III feel like real people in a realistic world. They have conversations that sound like human conversations. Character development isn't just about what's spoken out loud in dialogue. It's about nuances of performance and interaction, what people wear, what their apartments look like, so much else.
M:I:III feels like Alias the movie, Abrams, Orci and Kurtzman had just finished Alias and it showed, the plot is a thin retread of the first two movies. But Abrams does say on the DVD that they were trying to focus on Ethan the man, but his life mirrored that of Sydney on Alias, complete with house party and public action scenes. It's not a bad movie but it is a copy of the first two none the less.