I bought my Nikkor 35mm f/2 back in my Nikon D50 (a "DX" or crop-sensored DSLR) days and even when I upgraded to the Nikon D200 (also a DX sensor) I just never liked the quality of the images it produced. I can't explain exactly what it was, it just didn't do anything for me. I later bought a DX-sensored Sigma 30mm f/1.4, which is just the bees knees...focuses fast, is sharp and is a great all-around "normal" focal length on those APS-C sensored DX cameras.
Ever since upgrading to a Nikon D700, which is an "FX" or full-frame (35mm) sensored DSLR, the Nikor 35mm f/2 has been a star player! Again, I can't put my finger on what it is about the quality of this lens but, much like the Sigma sang on a DX camera, the 35mm f/2 is singing loud and pretty-like on an FX camera.
Plus McKenna makes it ever so easy to love this lens.
What's your favorite lens?