Hard to remember over 10 years what the games were that I played. I looked up a couple. Before I list my three I want to explain something … just because
Some games are high on my fun list and favorites but they are not games I would pick as games of the decade because they don't stand out. A food analogy I came up with explains it well.
Two of my all time favorite desserts are white chocolate raspberry cheesecake and peanut-butter and chocolate cream pie. I don't have them very often, maybe once a year, as they are rich, hard to make or even find (good fresh ones that is), and a treat.
On the other hand I also like oatmeal cookies. They are not special and rather common. But they are easy to make and have a lot of variety - for sweeteners use brown/white sugar, honey, or maple syrup; healthier with applesauce or yogurt, raw nuts, whole oats, and mixed grains; or more decadent with real butter, chocolate chips, and roasted walnuts.
Skyrim and Fallout 4 are oatmeal cookies to me. I have sunk thousands of hours into both and enjoy them immensely. Yet they are common - there really isn't anything spectacular about their story or game play (to me anyhow) except maybe for the companions in FO4 which I really like, especially Dogmeat, Mac, and Piper. Yet they are open-world games that let me mod, write stories, interact with the Nexus community, play with ENB and ReShade for screenshots, and very flexible … much like oatmeal cookies.
Yet they are not outstanding examples of game play for me so not going to list them here even though both of them I am extremely fond of and still play both of them fairly regularly.
IF I can count Dragon Age Origins, released 11/2009 so super close to 2010, then that would be number one (oddly this page lists it as 2010:
https://en.wikipedia.org/wiki/List_of_role-playing_video_games:_2010_to_2011).
Lastly I rate games on a gestalt - that is the fun factor made up of all the parts. I don't rate on some perceived quality or some checklist made up by some random players.
Anyhow my cheesecake and PB pie games would be:
1: Dragon Age Origins
2: Pathfinder: Kingmaker
3: Greedfall
Honorable mention to:
Pillars of Eternity 1 and 2 (this could be the third if DAO can't qualify)
Mass Effect 3
Of course there are many other games I have played in that 10 years I very much enjoyed (and odds are I might be forgetting one that I might list). But the above 3 finalists all stood out in some way - DAO because it was so new to me in style, 3D, companions, the story and lore … played the hell out of it and loved it and the companions. Pathfinder - because IMO its the next true Baldurs Gate game - so much intense attention to detail. Constantly finding new things, the choice and consequence blows my mind some times. It is so intricate and so many things you miss unless you do XYZ. I love how many paths there are and how many characters you can create from the options. Lastly Greedfall because it was so unique in story, lore, and setting. I simply found myself enthralled while playing. Also loved the companions.