Both were luxury coupes but my feeling is that the eight series were very different cars perhaps made for a diferent markets ( made mostly for U. S ? ).
1. It was much more expensive to buy, to own.
2. Weights much more.
3. V12/V8 engine instead of the classical inline six.
Of course both are great cars but very diferent IMHO. On the other hand I see the E24 was a worthy successor of the E9 3.0CS/i coupe. Let's see what happens with the future 6 series.