Is this a thread about the best boxset ever made or the best serious ever made?
In terms of pure value of epic-ness, Band of Brothers is hard to beat. The packaging of the tin is great, lots of in depth behind the scenes.
In terms content and re-watch value, Friends, 10 seasons, 24 episodes. It would be a while even before you start again from Season 1. I picked up a copy on DVD for £20, then picked it up on HD in Bluray for £90.
In terms of packaging, where do I begin, forget Steelbooks, I think Evil Dead came in a book with fake human skin leather thing, Kill Bill 2 came in a coffin that Black Mumba was buried in. Gilmore Girls came in something padded with what looks like a serious of photo albums, Spiderman came in a shoebox size include a copy of a comic that Spiderman first appeared in with a film cell, Twilight came in a jewellery box thing.