I think the easy answer is the 6 series because it's essentially the same kind of car, BUT fewer 8's were sold though and that makes it a more special car. The 6 is a rung down in terms of special-ness I'd say though I'd love to have one (650i 6-speed).
BMW needs to reinvent the 8 perhaps. They were the finest expression of the E34/E32/E36 era styling and still look great. The 850csi is near the top of my list in terms of ultimate awesome BMW's.
2008 328i 6-spd manual
2003 Audi TT Coupe 225