Home is where the annoying bard is
Hearthfire doesn't add quests or maps to Skyrim; it just adds the ability to build houses. (And to marry an NPC, and adopt NPC children, but ugh, who cares.)
The house-building project, though, is oddly satisfying; collecting the necessarily materials to erect and upgrade your mansion feels like a whole new mini-campaign, and the visual reward of exploring your house is even rewarding, in its own way.
Hearthfire doesn't add a whole lot to Skyrim, but what it does add is pretty, pretty good.
Better than: Saints Row IV: Enter the Dominatrix
Not as good as: The Elder Scrolls V: Skyrim - Dawnguard
Comparable to: base-building in World of Warcraft: Warlords of Draenor, but better because it's less annoyingly demanding.