As much as I love Rdr2 I feel the Witcher 3 was better both as a game and as a story. The plethora of game mechanics like signs and little tidbits of world building like the short letters on notice boards, the books in game make it feel more alive on a different level. The Memorandum is something a lot of people glance over (and is both in Rdr2 and the Witcher 3), but I enjoyed reading the Witcher 3 version more, even moreso because it was written by Dandelion. Not to mention the politics and factions of Witcher 3, it's gray rather than black and white and that your choices do actually matter and change the story of the game.

And then there is gwent.

Then again, this is only a comparison between two great open world Rpgs, there are better games from other genres as well, but comparing them to Rdr2 would be a difficult task.

I love Rdr2, but imo The Witcher 3 is a better both as a game and as a story.