i'm new to the forum and i think that in the us dutch bikes aren't very popular. also in italy isn't easy to find proper dutch bikes because they are expensive but don't look cool.
most of the city bikes or "holland style" you find in europeans shops are just strange mixture of cheap components.
the most famous dutch brands are: gazelle, batavus, sparta, cortina, in recent years azor.
many are now made of aluminum but it makes really no difference, are still heavy. the traditional models all have something in common:

-upright geometry (often with adjustable handlebar)
-28" wheels (good quality wheels)
-hub gears (up to 8 speed)
-closed chainguard
-roller brakes
-robust rear rack
-good quality paint
-fenders and rear skirt
-many accessories (soft grips, front dinamo light and rear battery light, bell, rack)

i like my gazelle, it's not a race bike and it's heavy, but has something like 15-20.000 miles and has always been stored outside and required nothing more than some tire changes. now i start to see the signs of the time, the bikes i have owned before would have fallen apart many times.