I would have to say I like the Lakeview Manor the most. (Retrievable from Falkreth) you get some nice bandit attacks once and a while to do some leveling and have a nice fight. I built the entryway and main hall of course but my add ons were the Enchanted tower for left wing, Armory for right wing, and Trophy Room for North wing. Completly furnished thanks to Lydia (housecarl obtained after one of the first missions in dragonsearch, where you become a thane)

When I first got Hearthfire, I got really excited about the idea of building a custom house. But I quickly got irritated when I discovered I was limited in how the house was built. I couldn't build the room I wanted with the features I wanted. If I wanted a kitchen, I have to build the appropriate kitchen room, not build whatever room I thought looked good, then make it a kitchen. And I had no choice over the placement of features inside the house. So now I build the house I want, then mod it to my needs. Sometimes I don't build the house at all, just buy the land and place a nice farmhouse there, with a big field for farming, etc. 

Mods are the beauty of the game. I found one that allowed me to build on a waterfall by the Abandoned Prison with the ghosts. It has a brewery and a windmill. It's like building in Fallout! (I also found a mod in Fallout allowing you to build anywhere)

Same thing exists in other Bethesda games, too.

If I remember right, that mod that lets you build your own place near the Abandoned Prison actually came out before the Hearth Fire DLC, but I could be wrong. I love modding, especially when it comes to the HF houses. Bethesda had a great idea, but the execution wasn't the best. There should've been more flexibility when it came to the placement of features and room designs. I like what they've done for FO4, though. 

Well put, friend.

Wasn't there one that made you high king? I think I installed it but I never really got into it, maybe I just couldn't find it's beginning.

I remember the High King mod. I never downloaded it though. I had read at one point Bethesda had planned to let you marry Elisif and become High King, but scrapped the idea at the last minute. I'm kind of glad. Even though I jest about how you should be a god and start your own era, at that level of notoriety you really wouldn't have much to do. A High King wouldn't be out adventuring. He wouldn't risk getting an arrow in the knee when there's a perfectly good town guard to send in his place.