My favorite cigar is the Cuban Partagas Series D #4 - but I live in the States, and it is very hard to get them. Which non-cuban cigar tastes most like the Cuban Series D?
I've always found the old Padilla Miami 8&11 robusto to be similar in style. You won't mistake it for a PSD#4 but it does have some superficial similarities as well as some Cubanesque character.
Ernesto Padilla is in the process of switching production of this brand from Pepin Garcia's factory to his own so you may have to poke around to find leftover stock.
I've often directed Europeans with this precise request to the Tatuaje Reserva J 21. It is like PSD in execution and palate stimulation. At 5 by 50, it's 1/8 longer though.
This is a question which I think doesn't really have a correct answer. Nevetheless...
The J-21 reserva (one of my favorite cigars) is Cubanesque in terms of finish and depth of flavor, but not taste. It's really not possible IMO to duplicate the taste of a Cuban cigar with non-cuban tobacco. Conversely, I doubt you could duplicate the taste of a Padron anniversary maduro or an Opux X with Cuban tobacco. Each country's tobacco has its own flavor profile.
I suggest you also try Pepin's Cuban Classic, the Camacho diploma and the Greycliffe Grand Cru pirate and Salomone. All of these cigars have complexity and a quality finish like a Cuban cigar.
One cigar I forgot to add to my list is the Gran Habano Siglo series. I find these Honduran smokes to be reminiscent of some of the milder Cuban cigars.