There's a very subjective element to this that has to be taken into account: for example, if one values durability, then one is going to claim the diesels; if one values performance, then diesels are out entirely. One's conclusion are only as good as one's value hierarchy.
From my readings, the w107/116/123 cars ended an era. Uhlenhaut and Sacco were designers for all of these. (Uhlenhaut and Bracq designed the 115s). The 80's marked the end of this great designing team.
The 108s and 109s were surely outstanding cars. The problem here is that there are so very very few of them left, and the ones that are left are nightmares in terms of financing maintenance.
Let me introduce a new thought: those 70s cars that are so frequently "dissed" have a LOT to offer for them. Let me speak of the 450 SE/SEL as as my primary example since I know the most about it.
Yes, smog lowered some of the performance specs of all 70s cars. But the 450s got around that by increasing the size of the M116 3.5 to the M117 4.5, adding 30% more torque in the process. My 77 MORE than keeps up with most every car on the road today. Would the small motors of the 50's or even 60's cars (6.3 aside?). And aside from that point, "high performance" racing was NOT the purpose of the vast majority of Benz cars; driver satisfaction was (which is why most Benzes are sedans - not sport coupes). Futhermore, the M116/117 is an incredibly reliable and well-performing engine - smog or no smog - with a number of documented million mile examples. And in addition to that, the 450s came out with marvelous modern features such as zero offset front suspension that is STILL the basis of Mercedes cars today! The 116 cars have so many modern design (body) and engineering (mechanical) features that they are fully at home with today's cars. You certainly can't say that about 50's models. And when it comes to build quality, the 116s don't take 2nd place to anybody (at least, not by more than a hair!). My doors shut with the same ironclad finality and watchmaker precision as the 60's cars.
This paragraph applies to ALL vintage Mercedes cars. One thing that seems clear to me from my readings is that the very production success of the 116s, combined with the fact that today's 4th and 5th owners often don't have the money to maintain them, is leading to the same demise that earlier Benzes have suffered from. These cars go and go - even when poorly maintained - and people of limited means are buying them up and driving them into the ground. Since their parts are so much more expensive than for, say, any American or Japanese car, they don't get the maintenance they need (which cheaper cars w/ cheaper parts ARE getting). This is a sad fact that is destroying so many of the greatest quality cars ever made.
Mark made a distinction between "rich" and "smart" that requires response. First, often times the latter greatly helps one become the former (rock stars and actors aside)! But if you measure intelligence by profession, than "smart" people were still the primary buyers of the 450 SE/SELs. According to the Road & Track owners' survey of Aug 77, doctors were the single largest group (1 in 5 were owned by doctors); engineers and lawyers were also very well represented. Clearly, throughout the 1970's, Mercedes was still making cars for "smart" people.
What I'm saying is this: there is a good case to be made that the 80's (change in design team) led to one letdown in Mercedes quality, and 1995 (the year Mbz reduced their design period from 5 to 3 years) led to another. Now, 80's/90's/00 Benz owners can argue with this, but there is a very solid link between the great cars of the 60's and the Benzes of the 70's. And what is wonderful about the 70's cars - apart from their more modern styling and equipment - is there's a LOT more of them that are still in great condition today. But you'd better buy them now while you still can, before they're flogged.
Here's pic of my old girl:
