Disclaimer, yes neither game has any similarities with each other. However, they were both GOTY their respective year with Red Dead receiving the most amount of awards. However, I alwayse felt that Mass Effect 2 should have been the defacto winner. I love how Bioware streamlined the experience and actually making it a blast to play, not to mention the amazing production and story.
I got a bit bored with Red Dead at times, but still a superb game.
So who should have won?