Birthright is the setting that I credit most with my continued fascination with D&D. At first, I dismissed the setting as "that place where you play as kings", but after reading through the booklets in the boxed set, I was hooked. No other setting has ever affected quite as much as Birthright. From the way you could run an entire game using the domain rules to the iconic and deep campaign world itself, Birthright inspired me.
If some company were to pick up Birthright and bring the setting into the D&D 3.5 era, add me to the pre-order list.
For those of you who don't know, Kenzer & Co. are coming out with "Hackright" for Hackmaster, which is about as close as we're likely to see, methinks. More's the pity.