Captain America vs Iron Man. This match up is like the Boston Red Sox vs the New York Yankees.
In the trailer for the movie which the link is added at the end if you haven't seen it yet, Its possibly going to be one the biggest Marvel movies yet. Steve Rodgers is told by Thaddeus "Thunderbolt" Ross who was the U.S. army general dedicated in finding and capturing the Hulk that
"You have operated with unlimited power and no supervision, that's something the world can no loner tolerate."
Steve does not want to have any restrictions and wants to do his job by operating freely but Tony Stark supports the Government and what they are doing, Tony says during the trailer that
"If we can't accept limitations, we're no better then than bad guys"
Captain responds "That's not the way I see it" and this difference between them is one of the main reasons why they are fighting in the movie.
As that happens there are other enemies in the such as Crossbones who if you remember was the former commander (Turned Hydra) of S.H.I.E.L.D. that was crushed by the building when he was fighting Falcon in Captain America: The Winter Soldier and was later pictured in the hospital alive! The other enemy is Black Panther who is looking not on anyone's side but is rumored to be looking for Bucky Barnes who was Captains best friend.Turned enemy. Turned back to friend.
Bucky who saved Captain from drowning in the ending of The Winter Soldier has been on the run ever since the ending of that movie until now. He has regained memory from the past and realized what he has done isn't good and is trying to make up for that by helping Captain out, while at the same time hes trying not to get killed from the people and probably organizations looking for him for what he did when he was being controlled by Hydra.
After this movie in my opinion the Marvel universe is going to be changed, For this movie people will have to pick sides and what we know for teams is Iron Man, War Machine, The Vision, Spider-man who is going to be played now by Tom Holland not Andrew Garfield, and Black Widow. This team is overall not that bad but Captain America's team which is Himself, Bucky or The Winter Soldier, Hawkeye, Ant-Man, and Scarlet Which who is one of the twins that was given powers by Hydra in Avengers: Age of Ultron.
In the scheduled movies coming such as Avengers: Infinity War Part 1 and Part 2 which come out in May of 2018 and 2019 and possibly Thor: Ragnarok which comes out in November 2017, we can get a look of the Avengers crew back together in a movie and in my opinion there is going to be a lot of hatred and tension between everyone and see a lot of trust issues between people on the different sides. But we wont find any of this out until all of the movies are released so now its just anxiously waiting and hoping time fly's by as fast as Quicksilver who sadly died in Age of Ultron.