As a non-native English speaker from Europe, I've been to north-america three times only. Canada and the USA are pretty awesome, although so far these cities were Vancouver+island,Montreal, Toronto, Quebec city, Ottawa, Seattle, San Francisco..maybe Toronto was my least favourite.
In Oceania, I thought Adelaide was pretty stale. Nothing worth of seeing, the nature is far out of city limits or non-existent, the view from mount lofty is poor, and I would even say the best thing there is a cheap flight out of the country. Air-Asia had postponed my flight which resulted in being two more days stuck in Adelaide, you can imagine the boredom.
In the far east a medium touristy city like Kumamoto was insanely disappointing. I expected it to be as great as any other nice city on Kyushu, like nagasaki, fukuoka and kagoshima, but it turned out to be a dull city plagued by heavy traffic in the town center, and the locally famous kumamon bear (mascot) was almost nowhere to be seen.
In Europe, Belgrade was downright a culture shock to me. It's like there are only wild cavemen there and the city had been struck by a massive tornado that sucked all the colours out of the entire area.
Paris the most overrated imho, wanted to stay a week, could only stay five but left after thee days. I have only been three times to France in my entire life, which speaks volumes. One of the three times was a visit only, to disney land and that only other time was a quick border crossing from the Spanish Basque country side.
The town of Sparta (Sparti) on the Greek Peloponnese may sound exciting, but really it is a pretence. Nothing to see there, just bored old males hanging around the streets all day long (I guess that what you get for killing off all the newborn girls in ancient history to get a legion of Spartan warriors
) and that statue of Leonidas has been only there since a few years to attract tourists. Don't waste any time there.
Although technically not in Europe, but asia or the middle-east; I didn't like Istanbul at all. I wanted to leave as soon as I saw it. Lot's of angry looking males giving you stinks, hardly any women to be seen, lots of stray cats, crazy traffic congestion, overpopulated, dodgy and dangerous and what not.