Is a bit hard to explain but both endings made feel like you did all this just effort to see this? I appreciate when a game has the courage to slap you in the face with your expectations and giving something totally different, but those two endings made me like crap honestly, I felt like I didn't do anything after all the trouble I went with these characters.
I'm not saying that those two games are bad for that in any way but they just left me feeling really bad. Though, I can enjoy a sad or bad ending if it gives you some kind of "peace of mind".
Like in Deus Ex: Human Revolution for example. In that game nothing good happens from the beginning, especially for the main character but at least when everything was said and done it feels that you accomplish something even if you didn't have much choice and even with that the game let me feeling kinda cold but the experience was so good and everything was put together so well that I didn't mind much.
In comparison to RDR.
In where Marston tried really hard to live a normal life to give his son a good future, but he gets betrayed by the people he helps and kidnaped his family and kill him. 3 years later after that you see Jack (the son of Marston and Abigail) in front of the grave of his parents now both death ready to take revenge by becoming what he and his mother didn't want to see his son becoming; The same exact thing as his father, in others words, a criminal.
Oh and some of the characters that you meet in your adventure with Marston gets killed by X reason or not being happy in the way they want.
You don't liked the ending? Well, bad luck because that's how it ends.
Like I said before, is a really clever way to end that story but I didn't like that "shit happens" tone that the story keep throwing at you by the end. And probably that also was my first and last Rockstar game that I'll play because RDR give me a great experience but ruined everything with his ending for me.
And SotC? To not make this post longer I'll say that I didn't like the way how tricked I feel after killing those Colossi just for one girl which ends with you being sealed away in a land that no one can enter again. I feel more sorry for Agro though. That poor horse made my cry like baby the two times I manage to finish the game. ;_;
And I better stop here. I don't enjoy writing walls of texts but I hope that explains why I didn't like those two endings. I also hope seeing more experience like this from you guys, the one from Divinity 2 that Cyril mentioned is pretty frustrating.