I love this game, and I agree with you on the history and the breath-taking and scenery, sometimes you can just explore for hours and see what you find. I also like how Rockstar set the game in 1911 (1914 when playing as Jack), when the time of the 'Wild West' was coming to an end as modern technology and the federal government began taking control of the frontier. The lawlessness and ways of old were dying out, replaced by civilisation. They call it 'progress'.
I couldn't believe the ending, I really thought John was going to take them all down, but when he stepped out I knew he had no chance, he was good, but even the legendary John Marston couldn't shoot down 10-15 Army soldiers before they killed him. I was hoping he would pull a whole 'Marty McFly' trick by putting an iron plate over his chest and maybe 'play dead' but it was not to be.
And poor Jack, lost his dad, then his mother three years later. Uncle was gone, and Rufus (the family dog) was missing but possibly also killed in the attack. I think it would have been nice for Jack to find Rufus alive, the last bit of family he has.
I like to imagine what he did after the main storyline was completed. I imagine the same thing but in just slightly different ways.
1) Jack searches the attic of Beecher's Hope and find the gold bars John found with the treasure maps, worth a fortune, and gets on a train (or maybe the boat from the opening intro scene) and head for San Francisco with Rufus to start a new life with enough money to do it.
2) Almost the same, except Jack finds the first treasure map and decides to follow it up, which leads him on his last great tour of the American frontier. Eventually, he finds all the treasure and then heads to Blackwater to catch the boat.
I think it is a great story, and still one of my favourite games. I sometimes wish I could create my own missions, characters and add new weapons, animals and places. The sequel has been announced, I believe it will follow John during his days with Dutch's Gang, so a prequel, and we will see how he was abandoned by them, met Abigail, and those BOI boys eventually taking Abigail and Jack as leverage while he hunts down his old friends.
Probably taken this reply on for a bit long, so I will end it here