I have thought about this for a while, what exactly it is about the ES games (and also the fallout game with the same engine) that makes them so compelling and feels so special compared to other games. There is of course a lot of different things, but when I thought about it there is one thing that sticks out in particular.
There are other rpg games where you can talk to npc:s do quests and play a character.
There are other massive world games where you can roam around freely.
But there is one big difference in the ES games and that is the interactivity with the world. That is imo what makes the games stand out so much for me, you really feel like you are not walking around in a world full of props you can't interact with apart from what the developers think are "important". I really noticed this when I am playing Witcher 3 now. Even though that is an amazing game you lose some of the connection to the world when you can't really interact with anything. You can just loot glowing containers etc, but that is it.
In ES games you can really pick up almost anything. You can go over to a table and look and pick up the individual objects laying on the table, pick up the plates and toss them away, grab a basket with apples and turn it upside down and see all the apples fly out and bounce over the floor. It really makes you care about the world so much more and makes the feeling of exploration so so so much more rewarding when you can actually interact with it instead of just observing things like they would be just dead "stiff" uninteractive props for you.
I write this because I hope Bethesda understand what they have here and the value and uniqueness of this and that they will never take this away from their future games. In the opposite I really hope they will make every game even more interactive. I would love to be able to interact with the trees when I walk through a forest, perhaps in the future with new tech you could break off individual branches and take them with you to build a fire. Maybe you could take "souvenirs" from your enemies.. like cutting off their ears and hanging them on a necklace around your neck. Stuff like this that really are not always necessary but makes the game feel so much more interactive and alive and really makes you care about the environment and what you can do there.
I think Bethesda does a great job with this, and I really hope they will never abandon it but just keep developing this further!