I think the ending was ok, however, I would feel more satisfied with living the rancher life, making my ranch a top priority, making it grow and expand a great home for me and the missus, having more kids, and if I ever got killed, for whatever reason, THAT would be when I start playing as Jack. The government didn't have to kill John, but the bastards did it anyway, that was a bitch-move...
Jack should've been a cooler guy, though. What fun is it to have played a bad-ass gunslinger before who went out like a man, and then start playing as his bitch-punk of a son, who's really... REALLY ugly, by the way. At the very least, have him look better than John, so we don't get so sad when he's lost forever.
I'd look forward to a sequel, but not with Jack. Go for another cool guy, preferably in an earlier setting. Just a few years would be nice, maybe you could run into John when he was young, shooting and robbing people with Dutch? I'd like to cross their path, if not be the one who got John straightened out, perhaps. However, in the sequel I'd like to see the ability to hang people, watch hangings of criminals, scalping, bows and arrows, sabres, dual pistols, an actual use for the fist fighting function, custom outfits, custom face, ability to smoke cigars, drink booze without just falling over when you're drunk, but a gradual drunkness, whores, marriage, having kids, and of course, getting an actual job, not just mercenary stuff all the time, but the ability to work in the area where you live, be it as a lawman, salesman, rancher, farmer, hunter, et.c.
That would make this more fun, in my book. Especially the hangings. That's why I bought the game to begin with, to hang people, like in the real west. Little did I know it wasn't possible.