RDR2 definitely takes the cake for just being able to just travel around without a purpose and still find shit to do, things to see, and just have a fun, pleasant time being there in the world. In the end game that is, before that you are a bit more limited with all of the SW closed off and such so there's some major barriers to just going where you want until then. But still what is available from the start is massive and dense with variety and content.
BotW wins out if you consider things from the get go. The no hard limits at all once you leave the Plateau is really something else. But the world is more hostile throughout due to Guardians roaming around that can really make certain areas super hostile and the world itself is less structured for just normal roaming around on horseback and demands more active climbing and traversal.
Spider-Man is unparalleled for just zipping around the city, but sadly I think it's brought down a lot by how stale the city itself. There's really nothing going on at the street level interaction wise and gameplay wise the game just is pretty weak when you're on foot. The way Peter/Miles controls and everything does not translate well on foot or even close to the ground at slow speeds at all except when in fight where you quickly lock onto enemies and flip around.
Ghost of Tsushima is pretty great to just roam around in too in the late/post game, but the world just isn't as reactive/interactive as BotW or RDR. So it's just pretty to look at and going around, maybe hunting some left over Mongols, but you can't hunt or find NPC AI doing cool shit or anything like that. So it's a pretty static experience, jaw dropingly pretty as it is. Best horse controls of the generation too which really helps.