Skyrim on its own is very much worth the money, as you can still get lots of game time on it. People with hundreds of hours in their saves still discover new quests and interesting locations.
Nonetheless, as VoluptaBox already pointed out, with a few mods this game can definitely become one of the greatest games in a while with very high game time count for your money as well as high replay value. Mods help with the replay value by providing everything from little details, DLC-sized questlines up to complete gameplay and visual overhauls.
A feature of Bethesdas games is that they are highly moddable and you can tailor them to suit your needs exactly. This is why I value their games a lot and it'd be a shame to pass up the chance of modding, given that there are a lot of really good mods out there.
I think the only game I played more intensively is Warcraft 3, which I still believe to be the best game out there, even about ten years later.
