Surely not THE BEST layout...
The Mini-Wunderland layout surely is one of the biggest layouts in the world. I dug around in the German texts - and here are a few data for you:
The whole thing is built in three sections, covering an area of 540 square meters (that's about 6000 square ft.!) More than 500 trains with 7000 cars are running constantly (when they don't derail or a loco motor burns out

), all controlled by computers. The majority of the trains runs on Märklin track with center contacts. Track length is some 5000 meters / 16700 ft, plus about 1000 turnouts and signals.
BTW: The 3rd section (under construction now) will show American trains on normal two rail track and DCC.
As Steam Donkey said, the H0 car system is stunning. Based on the FALLER car system but refined, they can run up to 300 multi-function vehicles. The star is the famous Coca Cola Christmas truck with 142 tiny (!) lamps (LEDs).
Apart from these moving cars there are 10.000 vehicles standing around. And the landscape: 50.000 trees, 30.000 plastic people (now THIS would be something for Jon!!!

), 3000 buildings, 20.000 lamps/LEDs and... and... and... Total costs so far are around 2.5 million Dollars!
CRAZY!!!!
Seeing all this, I'm impressed, but I'm not exactly carried away. For me the railroad shows the 'spaghetti bowl syndrome' - tons of trains chasing each other around without any apparent purpose. The speed is way too high and weathering is almost non-existent. In short: It looks very toy-like.

The moving model cars look much more realistic to me than the trains.
Perchance, last week I saw a TV feature about this Mini-Wunderland. They showed the US-part under construction. The guys just had received a pack from Walthers (contents: a few hundred locos and about 1000 cars!!!

) The camera showed them, unwrapping the kits. Sudeenly their jaws dropped, when they discovered that they had to finish most of the kits by themselves. And then they were really consternated, when they found out that some of the kits had neither trucks nor couplers. But then some of them made some rather silly remarks comparing this 'primitve American toy train stuff' with the 'high quality German Ready-to-run cars'.

Not exactly an example of 'political correctness', if you ask me...
Just the same: Should you visit Hamburg, have a look at this bombastic Mini-Wonderland. The entry fee of 8 Euro (about $9) is not too much, and it's great fun for sure!
But the BEST layout??? Without hesitation I'd prefer some of the layouts of our master builders here on the Gauge for that title!
Ron