First off as a long time Captain America its an honor to write this for everyone to see. I know many people weren't a fan of The First Avenger but to me it was a great movie. I admit there were some issues with it and could have been better but it was still a good film.
As a kid i never really lived near a place with many comic books or movie theaters (I usually had to travel to go see them) but once I did see these movies I was hooked. These movies transformed pop-culture into something that cannot be described other then as Beautiful.
MY ALTERNATE ENDING:
Steve Rogers buckles himself in and lands the plane on a really thick sheet of ice. The landing was rough and the first bump knocked him into the control panel and knocked him out cold. Howard Stark and his crew are searching for Captain Rogers comes across a floating piece of debris in the cold weather of the north.
Howard follows a small debris trail to the wreckage of the plane. He enters the wreckage, frantically looking for him. He hears the plan screech, knowing that the ice shifts constantly and enters the cockpit area. He finds Rogers, slightly wet from some snow that had broken through the glass.
"I found you old friend" Stark says grimly.
He calls down a crew member to help him. As they carry him out, Howard grabs Steve's shield (obviously knowing he might want it back).
Captain Rogers wakes up in a hospital, his head is throbbing, looking to see Peggy Carter.
"How long was I out" Steve asks.
Peggy looked surprised and says "Oh my! Oh uh.. few days, Stark will want a word."
Steve is a little confused and worries. "Aren't you glad to see me?"
"I am... but" she responds awkwardly "It's just.... Howard wants to see you now"
Steve sees she doesn't want to talk so he finds Howard in his laboratory. Stark greets him cheerfully and gets right to the point. He takes some blood and runs many other confusing tests. Howard eventually lets him leave, So Steve goes to see Peggy.
"Peggy Carter, will you marry me?" Steve asks once she opens the door.
"Oh yes Steve! Yes!" She exclaims "I'm sorry about the way I acted, I was just so shocked to see you for myself, well I was embarrassed and thought it was a dream. I heard you die Steve."
"Well" Steve begins "I couldn't leave my best gal, not without giving her that dance."
Flash forward several years:
Steve and Peggy have two kids, a boy (5) and a girl (3), then another on the way.
Flash Forward to Present day:
A lady with red short curly-ish hair walks into a museum, alone, through the Captain America exhibit. She looks at all the things Captain Rogers had accomplished. Like life before the war, Project Rebirth, WWII, Vietnam, the first man on the moon, the Cold War, Presidency and all the other things that had been a success due to Captain America.
"Why are you here Natasha?" A man asks.
"Well Clint, if we will be working with his grandson we should brush up on our knowledge." Natasha answers
"Well you know since its his grandson that only makes him around 33% the man Captain America was" Clint responds.
"We should be getting back, Fury will need us." Natasha says.
The two walk out to a jet that takes them to a ship in the middle of the ocean.
(The ending basically sets up the Avengers without Captain America. Where Clint wasn't brainwashed by Loki. Steve grew old with Peggy and had kids. Then later Hydra definitely has a bigger radius without him, the Winter Soldier never realizes his true identity and Coulson would not have been stabbed [Even though he's still alive] Captain America was the start of everything, The Hulk might not exist since he tried to replicate it, the whole army could basically be super soldiers if there was a General or someone desperate to get his hands on some of Cap's blood)