Here's the way I see how a plot could work for a series of four movies:
First movie: Origin of ONE superhero (who will be referred to as SuperA for clarity purposes) introduced in a world where there aren't superheroes that are alive, only in comics. Stirring the media and creating the idea for superheroes to exist in real life. Perhaps due to a recessive gene or mutation of DNA (like X-Men but on a much smaller scale, only one person being the 1 in the 500 Billionth to get it or something). But this would be on a global scale, rather than just one city, the whole world would know of the existence of SuperA. It would also be more about the psychological aspect of being a Superhero, choosing good over evil, making some mistakes and going a little too far with some things but ultimately choosing to restrain himself and do the right thing, and all the baggage of the normal life he has to leave behind. With the conflict obviously being Man vs. Himself, perhaps the end could even be the end of SuperA, saving the world by sacrificing himself to stop a realistic end of the world scenario from happening rather than a super-villain causing it. Also, the movie would have cameos of future superheroes (such as being at the scene of SuperA in action that inspires them or something) and antagonists as well as future plot elements (such as how other heroes could become super like him leaving behind DNA for a scientist to experiment on or a him being a blood donor or bone marrow donor which causes the recipients to gain powers) but it would have a plot in itself and a satisfying ending rather than a cliffhanger.
Second movie: Takes place within the time frame of the first movie but only has brief scenes from the first, perhaps a different point of view of something happened in the first movie to be the beginning of this one. This one would feature two characters, one inspired by the SuperA to do good with the powers (SuperB), the other inspired by SuperA but warped and sees things at the wrong angle (VillianA). Each of the characters rise to fame as they create secret identities unlike SuperA. SuperB and VillainA both start out helping the world, but VillainA begins to go to far in stopping crime, his descent is a major arc in the movie. This causes SuperB to confront him, becoming the major conflict for the second movie, giving way to the idea of Superheros vs. Supervillains. SuperB wins but VillainA escapes. Throughout this film, cameos continue to occur of others who have gained superpowers and are inspired to choose a side, perhaps during the end a news report could be describing the events caused by the two capes and flashes of a few people using superpowers for either good or evil privately to give way to another movie. This ending would have a satisfying ending but would still have an underlying cliffhanger.
Third Movie: In this one, the timeline will begin where the other left off, giving a few days for the preceding flick's events to settle. VillainA, realizing he's not a match for SuperB, goes undercover to search for more superpowered beings like himself. SuperB continues to do heroic things, but is being bombarded by media and a large amount of people become overly obsessed with him. Wishing for a companion (I know cliche) he begins secretly looking for others like him, as well, publicly announcing his search and tipping off the other heroes with abilities. However, SuperB has no luck as too many fans just pretend they have what it takes, whereas VillianA finds a few to join his cause. All the while, the story mainly surrounds SuperB's failing focus and begins to make mistakes in his missions, emphasizing his need for someone to lean on, another two superpowered good guys are in scenes throughout the movie, doing small acts of kindness with their abilities, but nothing at the scale they could be doing, like SuperB. VillainA's scenes are very short and sporadic throughout the movie, only alluding to the growing danger of this criminal league to SuperB. In the end of this film, SuperB is up against a rather titanic natural disaster and has no hope of saving the people in danger on his own, cue the other two heroes. In the climax, the heroes work together to save millions of people from the disaster. Afterwards, SuperB and the other two talk and they decide to join SuperB in his heroics. Paralleling and contrasting the union of the good guys, VillainA is speaking in front of a group of characters (some brazen and others a bit uneasy) and discussing the power they can have and the better world they could create if they work together to destroy SuperB, without knowledge that SuperB has just added heroes to his cause. This ends with a major cliffhanger to lead way for the final movie. At the very end or after the credits: a scene of someone in a hospital bed revealed at the last second to be SuperA.
Fourth Movie: Time jump into the future. Flashbacks lead up to this point. This movie will be the climax of the entire four movie series and a major showdown between the forces of good and "evil" (which have both gained multiple more members), each side claiming to fulfill the legacy left behind by SuperA. Epic battle ensues, much like a guerrilla warfare tactic. Some good guys are killed, some bad guys are captured. Each side becomes to focused on stopping the other and start causing mayhem and destruction in order to defeat the other side. In one final battle they have all gathered in one major city and the city is being wrecked from their fighting. US Military intervenes to stop them from fighting to keep order but to no success, so they start picking off everyone that has powers, some killed by the military and some killed by the opposing side. In the climax of the battle, when most of the heroes are unable to fight, save for SuperB and VillainA, they both are stuck in an embrace that is causing a built up of energy, but unwilling to give up, both pay no attention to the clearing landscape from the energy, nor the person who is coming to them from the sky: SuperA. However, he is a tad too late. As he's rushing to get to the two the energy is released and destroys the city around them. Bright White fades to black and then point of view of SuperA waking up. He stands and sees SuperB and VillainA lying in the middle of a large crater cause by the explosion. Going to hem, he sees they are still alive, as they get up, see each other and continue struggling, however, they are powerless. SuperA still has his powers and intervenes to restrain them. In his struggle to restrain them, SuperB kills VillainA somehow and SuperA gives epic speech on what being a superhero really means as the dust clears around them and the remaining superheroes and villains gather around to hear a call for peace (perhaps this could be planned out better but to an extent, something like that.) The End.
This is just rough idea, I'm sure I could write something much better if I had more time. But this is just an idea of what Hollywood could do with original superheroes.