Of the Rokkor, FD and Zuiko I'd say that the Rokkor MD 50mm has the least character, is the most transparent and gives the most modern look being sharper and with a touch less ca on bright areas, next the FD and third the Zuiko but I'm really only looking at differences at the widest apertures and for example if you apply a bit more sharpening and contrast to the Zuiko the gap between it and the Rokkor narrows.
Other than f1.4's for character the Rokkor 55mm f1.7 MC takes some beating, maybe the less modern coatings add to the character. This is the lens that got me into old lenses and it does IMO give a special look, the way he sharpness and dof falls away across the frame does IMO give a different look. I also like the Rokkor 50mm f1.2 MD as it again has a special look at wide apertures but stopped down it's just a nice lens which really gives you two lenses in one, modern and transparent looking stopped down and with its own look at wider apertures. I tend to like lenses with dual personalities or maybe even just a different look. Another one to look at is the Rokkor 50mm f1.7 MD as it's small, light, sharp and like the MD f1.4 gives a more transparent look. I have the similar FD and Zuiko f1.8's and I'd place them in the same order, Rokkor, FD then Zuiko.
I also have Nippon Kogaku 50mm f1.4 and f2 but IMO these don't match he others I have. The f1.4 in particular is very characterful and dreamy at wide apertures and really these two lenses are more about character and build quality and the joy of using them than wide aperture performance. I've taken some of my favourite pictures with the f2.