How about the quality issues with respect to sigma? Peeling, inability to focus correctly except for sharp copy, and after changing cameras?
"They are cheap and mass-manufactured and failed often". Soon forgotten. How many sigma lenses will we remember in years to come?
I've used several Sigma lenses and they still focus correctly. Peeling? Sure, which is why Sigma stopped using that layer a few years ago. Sigma is innovating right now with lenses and features Nikon does not have.
You think Nikon lenses have no issues? Try reading a bit more. ;-)
Also, one thing to note... it's not LENSES I would want to be remembered for, but rather images, and Sigma lenses can give you images as great as Nikon lenses at a cheaper price, and also have lenses you will not find with Nikon. If all you care about is how memorable a lens is, then you're more of a gearhead than a photographer. Gearheads will ask "what lens/camera/setting" while photographers will simply admire the image artistry.