I know it's not fair.
However I am not too impressed by the E34 M5. Yes the E39 540i and M5 are probably nicer than the E500. However the 540i is almost common in Boston and the 500E is still a rarer sight than an M5. Not to mention that an E39 M5 could get me two and a half 500E's
The M6 looks better than both the E39 and E34 IMO. The E24 and E31 have been long time dream cars for me just like the W124 500E and I'm just trying to get one of 'em. The M6 I was interested in just happens to be around $10k (less than actually) and it's in Black/Black with 18" BMW BBS rims. The car just looked so beautiful...
The E31 just seems too expensive a car to maintain. I'd take the V-12 850 with 6-speed over a 500E if I had the cash to maintain it though
Don't tell me it's not a fair comparison again. I just think that these are the rarer MB's and BMW's and i like cars that way.