Back in 2008, Marvel did something that had never been attempted before: at least, not on this scale. They made the decision to make the series of superhero movies they were planning to all take place in the same shared cinematic universe. Yes, in the Marvel comics, Iron Man would occasionally team up with Captain America to fight the bad guys, but that's fairly easy to accomplish: after all, it's just pen and ink.

But in the movie world, thanks to things like actors' schedules (and salaries) and that Marvel had licensed some of their characters to other production companies, it was a lot more difficult. Yes, Spider-Man (Tobey Maguire version) was technically in the same universe as The Incredible Hulk (Ang Lee's "Hulk"), but because the first was produced by Sony and the second by Universal, there was no way the two would ever be able to work together.

But that all changed when Marvel created its own production company. The Marvel cinematic universe currently includes the three "Iron Man" movies, the two "Thor" movies, "The Incredible Hulk," "The Avengers" (and upcoming "Avengers: Age of Ultron"), the two "Captain America" movies and, of course, the "Marvel's Agents of S.H.I.E.L.D." television series. The upcoming "Guardians of the Galaxy" movie is also part of this world, and they have four more movies planned currently. (Plus, they keep promising us that "Black Widow" movie. Take my money now, please!)

READ MORE: Film Review: 'Marvel's The Avengers'

Having a shared universe means that the movies will inevitably be compared to each other—more so than usual. The "Iron Man" trilogy is more your basic action movie setup, inspired by James Bond with the technology and character of Tony Stark. Meanwhile, "Marvel's Agents of S.H.I.E.L.D." is your typical procedural drama, just with a superhero twist. "Thor" is almost a soap opera, the plotline so Shakespearean it made total sense to be directed by Kenneth Branagh, while "Thor: The Dark World" tipped more into the fantasy world that would also see the home of "The Hobbit" trilogy. "The Incredible Hulk" is more your science fiction mutation plotline. The first "Captain America" is a nod to the World War II adventure films. And "The Avengers" combined all the best parts of each of the previous movies into one beautiful piece of poetry.

"Captain America: The Winter Soldier" is a bit different: less of a straight up action film and more of a spy thriller like the Bourne movies or "Mission: Impossible". It's compelling and tense, but makes sure to use humor at the right times to punch through said tension. With a plot that builds on the thin line of wanting protection but wanting freedom, the story isn't exactly new: you see this same dynamic played out in "Watchmen", among other movies. But it also deals with the issues that were left open at the end of "Captain America: The First Avenger" of having a man who lived in the 1940s dealing with the world of today, and notes the concept that Steve Rogers would have one hell of a case of PTSD.

Without a doubt, "The Avengers" is by far the best so far in the Marvel cinematic universe, but the two Captain America films are both worthy of vying for the next spot. As far as sequels go, "The Winter Soldier" is hands down much better than "Iron Man 2" or "Thor: The Dark World". Both of those, while not terrible films, seemed flat and bland, everyone showing up because they had to rather than they wanted to. "Iron Man 3"gets a bit more on track, and Ben Kingsley absolutely makes that film worth watching, but still is much more of a sequel than a continuation of the story. "The Winter Soldier", on the other hand, is more a movie that just happens to share the same characters of "The First Avenger" and follows their storyline even further.

It's definitely a separate movie, and that makes it work.

Contact Staff Reporter Angie Fiedler Sutton here, and follow her on Twitter.