A lot of Suntour stuff did not just go on department store bikes, a lot of low end Suntour stuff did as did a lot of low end Shimano stuff. Once you got past the Seven line of derailleurs the rest could only be found on bikes sold in LBS's. But like you said even the low to mid end Suntour stuff shifted better than the top of the line stuff sold by Shimano or Campy after the slant parallelogram derailleur was introduced. The higher end Suntour used the same slant parallelogram design but they went further with using lighter parts and better mechanicals. Once you got into ARX, Cyclone, Sprint, Superbe, and the Vx series those were mostly LBS's offerings. There were some exclusions to that, when Nishiki and Centurion started to piss of LBS's and selling their bikes to retail stores some of those came with the higher end Suntour but I don't recall if any of those ever had Superbe or Sprint. For the most part Suntour mid level on up was mostly sold in LBS's.

Miche was not that great either, they lacked in quality until sometime in the 80's and 90's they rebadged Suntour derailleurs with the Miche name. Mavic wasn't all that great either, they were made by Simplex! So to say Mavic was better then Simplex is pure ignorance of the two models.

I think the best French made derailleur was the Huret, the Jubilee and Duopar was virtually indestructible and it shifted better than the Campy and Shimano of the day, and the shift levers were the best levers ever made by anyone. And you also have to keep in mind that until the slant parell. design by Suntour came out all, and I mean ALL derailleurs were crappy in function, but that's all there was so you went with what you had, after that companies strived to make the derailleurs better and shifting quality eventually went up in all brands but it took quite a few years probably not until Shimano SIS came out was there any measurable improvement. Sach/Huret came out in the early 80's, to say early 80's bikes are not vintage is just not right unless in your mind anything newer than 1979 is not vintage. But it was in that age of Sach/Huret that a truly classic Duopar derailleur came out, the finest French derailleur ever made.

As a side note, I have two bikes with the newest STI (2013 105) and Ergo (2006 Athena) shifting systems, and I test rode Dura Ace and Ultegra, and none of those shift faster than the SIS did! SIS is just faster for some reason, I push or pull the lever to the next click and bang it's in gear, with STI or Ergo there is a slight delay and a slightly softer engagement, plus with SIS I could shift from first to 7th and bang it's there right now, not so with either of the other newer stuff. In fact my friction Suntour Superbe non indexed shifter shifts as fast as my newer stuff! I'm just saying what i've experienced which I'm sure most of you will disagree, after all how dare the newer stuff be rated below older stuff, it's sacrilege.