OK I'll bite.
Nothing has ever felt as good as my 1974 Jack Taylor -- but then, I've ridden it for 32 years and for most of those years it was my only bike, so we had ample opportunity to become comfortable with one another.
In recent years, I've found a few others...
My 1981 Stout The 1977 Richard Sachs I bought and built up this year My off-topic 2002 Merckx Fuga
Having answered the question, let me throw in a BIG caveat: Over the years I've come to appreciate how even seemingly slight adjustments in how a bike is fit to me can make an enormous difference in my comfort -- small changes in saddle height, forward-aft saddle position, angle of the saddle's nose, stem length, handlebar width, crank arm length, and so-on (not to mention how a particular saddle fits my rear!). I can't judge how much of the "nothing feels quite like my" feeling that some bikes have compared to others is simply due to some bikes having, by chance, had the various adjustments set in such a way that they fit me better. Perhaps some of the bikes that feel not quite on, simply need a small adjustment.
Please don't misunderstand -- I am competent at setting my saddle height, and generally matching the overall reach. I use my preferred length cranks when I can (I've found that I strongly prefer 180s for my 36" inseam legs, which I can't always get in a particular gruppo), etc. But when you throw in the subtleties of how seat tube angle, head tube angle and so on effect the other adjustments, how many of us are really experts at fitting? I suspect that, like me, most of us, at best, get close, but maybe don't know how to get it "spot on".
And I suspect those minor adjustments make a huge difference in the feel of a bike and thus the "nothing quite feels like" sensation.
So perhaps if I knew how to make the subtle adjustments to get each bike as "spot on" as it can be, many more would have the "nothing feels quite like" feeling -- or at least I'd be more confident that I'd given each a fair shake.
David
David G. White
Burlington, VT