I'm going to have to go ahead and disagree with the author's choice. The Negroni? I mean, don't get me wrong: I _love_ a good Negroni. And we may well want to pose the pregnant question of what in the world we mean by a "perfect cocktail." But if the criteria of broad appeal is central, then the Negroni is out like a brown shirt in the spring of '45. If I had a shilling for every time someone ordered one based on its color, only to pull a curdling grimace on the first swig and demand a something-tini in its place, well ... I'd have at least a few schillings. Possibly enough to buy me a Negroni.
Campari is a wonderful amaro, but it is an acquired taste on the order of Islay scotch, if not beyond. And in a society of palates trained predominantly to the hooks of the pleasure trap, bitter is the odd man out on the flavor quadrant. Sorry, escarole, and sorry Campari too.
It's not a problem, of course. The celebration of acquired tastes guarantees us delightfully uncluttered avenues. I just don't see the value in pretending such a stinky cheese is going to be a crowd-pleaser.
And speaking of crowd-pleasers, I'm going to have to say bravo to all of you. Every single one of the cocktails proposed makes a better "every wo/mans" cocktail than does the Negroni. The White Spider, the French 75, and (biases declared) the Dark and Stormy are my exemplars.
Against my better judgement, I'll submit the (fresh) margarita for consideration, as it is remarkably popular despite its broad range of flavors offered. As it contains tequila, it may well lose critical volume in terms of appeal. However, anything universally appealing is bound to achieve such only by sacrificing intensity and nuance. Hence, pabulum. So, in short, the quest is broken (which makes it that much more fun to pursue.) And upon that broken quest, I'll pour my margarita.