Skyrim was quite fun without mods as I enjoined a bit of travel in the world, then once it got repetitive I ran through the main story and finished it. After that, deleted the game.

Playing through Pillars of Eternity, without mods, having a lot of fun, if I had the time I think I would have just set for 2 weeks, 8 hours a day to finish it :)

On the other hand, Neverwinter Nights, which in my opinion was the best game ever created, had a boring Single Player mod, which I've never bothered to finish. However, this game was not created for it's single player, the single player was created to show-off the tool-set. The game inspired an amazing community of modders, story tellers and players. From hard-core role-play driven persistence worlds (mini-mmos which are actually story driven, controlled by players and effected by players) to role-play groups that played together on private servers. The game wasn't limited to RP, it had social servers, PvM servers, PvP servers. The game wasn't limited to servers, there was a very active community of moders that created extensive single player mods, some of them were better then paid game.

The modding community brought the game to it's limits and behind as coders created software to by-pass some of the game limits. Even after the main servers were taken down, some people are still playing the game, they created replacement for the main server.

Even though I'm not playing anymore, I think that NWN was and is better with mods, as it was design to be such a game. It saddens me that there is no modern replacement. But there is a problem with modding modern rpgs, games like Skyrim are so complex from the visual side that the bar for creating your own environments is much higher then in NWN. Which means that a single moder, or a small group can't just create a map to tell their story.

I hope my message makes sense in this context, I think that rpgs with complex stories like PoE when they are well made are in no need for mods. Skyrim, which has a simpler story but focuses on creating an open world can benefit from mods, but due to it's complexity limits the type of mods that a single and pairs of modders can create in their free time. I think NWN was in the middle, simpler graphics which meant easy map creation, but a strong tool-set with a strong scripting language.

I miss NWN and sadly no game was created since which, in my opinion, balanced so good around mod creation.