OK. It's true I haven't seen much from the 2nd-5th edition stuff, but after careful consideration of my collection, here are my nominees:
Huso's A Fabled City of Brass --- I think it is visually striking in an amazing consistent way. Well labeled sections, and almost the platonic ideal in it's use of inset maps. Where it probably falls short IMO is in the organization of text within each keyed-entry. It doesn't ramble, but there is no clear format (use of bold, bullets, etc.). Leveraging his background in video game design, Huso created a polished gem. If this were solely a beauty contest, he'd win hands down.
Fullerton's Many Gates of Gann --- There's a reason this publication keeps coming up in conversations about "how to do right". Not only is the content fresh and exciting, the presentation is modern and well laid out. The editing is tight, with little to no fat. The maps are great too. Everything is just there, at-a-glance, with great use of sidebar blocks. Eight years after publication, it still remains a high-water mark.
Lux's Castle Xyntillan --- This thing is huge, but the way it is broken down is so intuitive, it's easy to understand. The text is quick and to the point. Whereas Huso's City is lush in color and presentation, Castle X is minimalist black & white --- reminding us the game is to be played at the table, not at the reader's fingertips. The use of bullets and indentation is formidable, so that---despite its OSR look-and-feel---it's a modern document. My one quibble would be that I think it could have benefited from a denser type-setting. Both the font-size and large margins means few entries per page, which I believe makes it marginally harder to absorb (and find) information and discern its structure. All in all, this product deserves all the praise it has received and makes you want to play D&D tonight. Hat's off to Melan.
Hawkins' Darkness at Nekemte --- Looking at this one more closely, I am going to proclaim it my "winner". The font/layout is modern, and I believe it best internalizes the Bryce-ian design principles through it's evocative descriptions, summary tables, inset maps, and cross-linking of expositional sub-paragraphs through bold text. The black & white artwork perfectly compliments the content. Everything is tight and crisp. My one nit (and others contenders fail here too) is that the keyed text precedes the map. While I am fine with maps-in-an-appendix, much like walking into a museum --- I want to "see" the thing first...then you can go into all the little detailed descriptions. Map-before-text ... ALWAYS. Although smaller, I think Nekemte is a notch above its mega-dungeon cousin (Gunderholfen)---more focused too. Clearly Hawk learned a bit on the first one, and is now hitting his stride. WINNER, WINNER, CHICKEN DINNER.
An honorable mention goes to Chainsaw's Lost Treasure of Atlantis, but we all know how his publishers tripped him up on format. The content, non-linearity, and multiple connected location is pretty much the type of adventure I wish I was producing. The Monkeyblood Design (Glynn Seal) maps are world-class too.
So that's my short-list for the best of the New (Old) School. These are the places I hope my players will go some day, but I haven't been lucky enough to really kick the tires.
I also think there is room for improvement. "The Dungeon" works organizationally because of its compartmentalized nature. I haven't yet seen Arden Vul, but so far I haven't witnessed anyone really nailing down the problem of multiple levels-of-detail. I'm still waiting for the product that effortlessly contains all the layers of the campaign onion.
Lastly, this wasn't a content competition (as originally asked). If so, more of Matt Finch's stuff would probably have made my list.