Teeny tiny circles of confusion.
The right kind of bokeh, whatever is the right kind.
Good chiarascuro or however you spell it.
Dmin (sort of the anti-Dmax, like yin and yang).
Good saturation but not overblown "Disneyland" colors.
The right aberrations for that old timey "glow" that only comes from old beat up low quality lenses, crusted with motor oil, spilled beer and cigarette tar.
The look of old films we can't get anymore, printed on papers the corporations keep planning to discontinue.
Anything and anyone, if enough booze is administered.
But seriously, I have no idea why some things strike me as beautiful or ugly. Analyzing them makes no difference. I don't like Picasso paintings. I don't know why. Either I immediately like something or I don't. If I have to analyze it and convince myself that I like it, then I guess I really didn't like it after all.