StingingVelvet: I honestly don't see enough of a difference to set them apart, but since you asked...
I'd say Gothic 2 or the first Risen. I'm honestly not a big fan of The Witcher 3, I find it too directed and simplified. I felt like I was just going from one map marker to another instead of exploring naturally or doing any interesting quests. I know I'm in the minority, but it is what it is. Gothic 2 I haven't played since it came out, but I remember loving it at the time. Risen I also liked a lot, and it's probably more polished, so maybe I'll go with that.
I'm looking forward to play Elex sometime soon.
I truly believe that Gothic 2 NotR has the best exploration in RPG. Every plants, every animal killed (exp), every stuff, count. But at the same time gameplay isn´t become in looter cave exploration - as in TES - because the world have consistency and internal logic. I love the Gothic feeling when you have to enter deep into the wood, and you too weak, and you have to find out how you can do it. You can ask for help. Old friend. But what after you get you looking for? You back to safer zone, or your risk and go deeper alone? Just because ther could grown extra rare plant or you can find something you cant buy or find in merchants. Thats atmosphere 11/10. I love Witcher 3, I love exploring it, but in thats regard nobody beats Gothic 1/2. Its a shame Gothic 3 was such a mess. A tragic end to franchise.
Elex is a nice game, i have like 140 hours in it or something like that. If you expect magic of first Gothic you won´t find it, Elex its far behind. But its still a solid 7. And if you fan of Piranha Bytes RPG, then perhaps even 8-9. Hovewer, as I recomended you try Elex, i recomended you even more Kingdom Come. Is like Gothic 2 get married with Witcher 3, and they have babie. And that babie is called Kingdom Come.