My list:
Witcher. What I loved about this game series from the begining with was that it didn't want to offer you the typical high fantasy setting with clearly set lines between good & evil. Right from the prologue, it forced the player to make morally ambiguous choices and then it delayed consequences so he could not just reload to see the best outcome. In addition it was just expectional how the main quest was carelly revealed through each chapter. Sometimes it even seemed like an afterthough, but every chapter actually pushed the story forward in some intresting manner until all if it came together at the end.
The Witcher 2: Assassins of Kings. It was really impressive how choise & consequence heavy the three chapter long story turned out to be. Quite remarkable how some choises in chapter 1 could alter the entire course of game so dramatically. I wish we could see more of this kind of reactivity in rpgs.
Witcher 3: Wild hunt married open world gameplay with cinematic storytelling really well. Such a great triumph to Witcher trilogy. Compared to witcher 1 & 2, I think the story focus was shifted from politics to more personal level and back to good old fashioned witcher work seen witcher 1 without forgetting great character and quest writing from Witcher 2.
Dragon age orgins hit all the correct notes for me. A great spiritual successor to baldur's gates and just like them, DaO was better than the sum of it's parts. Bioware's best game of this era.
Skyrim. I'm just too ashamed to write how many hours I've logged trekking Skyrim's vast landscape… The best open world rpg of this decade and the second best TES game as well. Right there after Morrowind.
Divinity orginal sin 2. Really enjoyable turn based combat, rich and dynamic gameworld to explore, great ammount of freedom to solve quests, good writing, fun companions…what is there not to like?
Fallout new vegas. I haven't played fallout 4 yet, but compared to Fallout 3, new vegas felt like a proper Fallout game. Obsdian just understood Fallout mythos better than Bethesda. I liked that it was more serious and not like a post-apocalyptic theme park.
Deus Ex: Human revolution. The orginal deus ex is one of my favourite games of all time and after the horrible Invicible war disaster I began thinking that the series was dead. Thankfully they managed to gracefully revive the series. The dev-team really captured the essence of deus ex and created an orginal new entry to the series.
Mass effect 1. An other Bioware game which brings back many good memories. It was just amazing to play through the entire trilogy with one character and experience how my choises determined the fate of my companions. That all being said if I'm forced to choose one of the ME trilogy games, it has to be the first mass effect. While I really enjoyed playing each one of the trilogy games, the first mass effect defined the whole universe and let me really explore the galaxy in its truest sense.
Elex. I'm still in the middle of it, so I'm not sure if it is a bit premature to raise this one my list, but Elex is just a darn fun game to play. Piranha bytes have finally been able to set aside poor risen sequels and release a rpg worthy to gothic series.
Few others that just didn't make on the list, but deserved to mentioned:
Risen 1. I think it is tragic that piranha bytes were so close of creating something special. Despite weak sequels, the orginal Risen is one of the best open world rpgs of this decade. Had there been no Elex, this would be on my list most definitely.
Pillars of eternity. I was really happy to pledge this project. I know this game divides opinions a lot, but for me it felt like classic era infinity engine game and I really enjoyed exploring the rich dark fantasy setting Obsdian had created.
Tyranny. I thought this was a very clever small budget rpg. Really cool idea to turn tables and force player to play an antihero in a world where evil had won.
Age of Decadence is a bit rough gem, but it really deserves more credit. It is a punishing rpg to play, but becomes quite rewarding once you unlearn all the "bad" rpg habits. It was so refreshing that in this game I'm just one guy who tries to make the ends meet and survive. The fact that the world just doesn't revolve around my sorry ass is a very stimulating feeling which is too rarely encountered in rpgs. It is not the longest rpg out there, but there are an insane amount of different ways of completing it. To get full picture, it is really worthwhile to go through it with different characters.
I can't say that I often enjoy playing blobbers, but Might and Magic X is just an outstanding rpg.