It is so difficult to put any single place as a favourite as they all have their merits.
While I haven't visited everywhere in the Uk I have been lucky enough to see most of the great prehistoric landscapes and every one has left me with a stupid grin on my face that has taken at least week to remove.
However, I have been fortunate enough to live in North Wiltshire area for most of the last 44 years and I never tire of visiting not only Avebury but all the places within an hours drive of my house. There is so much to see on my doorstep it is no wonder I have never moved and never wanted to.