Originally posted by pepperberry farm same here - I also do searches for photos by specific lenses on Flickr....
And yet, when a forum member posts a blind comparison between lenses, I often have a hard time telling a 50$ from a 500$ lens...
Apart from obvious, easily measurable things like the number of aperture blades, maybe much of the difference is in how a lens performs over a wide range of situations.
I have no problems getting nice pictures from the 18-55mm, but that's because I use it at least at f/8, if not f/9.5 - unless the alternative is to raise ISO over 1600, in which case even wide open is fine.
People get to know their lenses over time. You look on Flickr and get a hand-picked selection
Then there's the subject, the light, the camera you used...
So, I don't know... this whole lens business is difficult to understand well...