Nintendo

If you can play 5 on anything other than the Switch I would do that for performance reasons. Otherwise I think it really depends on whether you want a top-down view or a 3rd person 3D one. If you are okay with top-down, go with RF4. If that does not appeal to you at all, RF5 is still serviceable on the Switch, but watch some videos to make sure you’re okay with the performance.

If same sex relationships are important to you, RF5 is the only one that allows it. Otherwise just pick the one that’s more visually appealing to you. If you go with RF5 first, you won’t know what you’re missing from RF4 and can still go back and play it at some point in the future.

hi everyone, thank you! i ended up getting 4 on the switch :)

a bit late but yeah 4 is great. Rune factory 3 is also great, but it might be a bit awkward to go back to since you're playing 4 rn. Rune factory 1 and 2 are in a weird place to me. They're fun for a first play through but 2 in particular has that issue where the characters don't have much character and there is a lot of repetition. Rune factory 1 especially is still worth playing through at least once even if they're very rough compared to the later games.

I have only played RF4, and it's a really fun game. The game has tons of content, and there is kind of a story to follow too. With or without the existence of RF 5, I would recommend you play RF4. Run Factory 5 isn't going anywhere, you can play it couple of years down the road.

And as @zazh@laguna.chat mentioned below,

RF4 is also on Xbox and PC Gamepass, as well as PS+

I enjoyed 4 more. The town and characters feel better in that one. While in 5 the town is so big and empty. Though gay marriage is only in 5 if that matters to you.