Comparisons to GTA 4 and 5.

All three games tend to have a few things in common, save from murder and theft. John Marston is a combination of Niko Bellic and Michael De Santa. He arrives in New Austin, seeking out an old accomplice, as Niko was doing when he came to Liberty City. But John is being blackmailed by the federal government to rat out the old gang he used to run with so he could do straight, as Michael did at the start of GTA 5. Throughout the game, John encounters oddball characters who help him, but only after he does something for them. Same with Niko. With each completed mission, it brings the protagonist ever closer to finding the people he seeks. The same thing happens in GTA 5, except in reverse. Along the way, in addition to allies, the protagonists also meets slimy villains who later betray them. (Dimitri in GTA 4, De Santa in RDR, and Devin Weston in GTA 5).
Finally, Niko and John meet up with their respective quarry and are given the choice to kill them or let them go, though in John's case, Escuela is optional, but you have to kill Williamson, and in GTA 5, killing the villains is optional, depending on whether or not you choose Ending 3.

Too bad RDR and GTA don't exist in the same universe. I mean, they could. All references to New York could've been changed to Liberty City, California to San Andreas, and so on.