I must have bad taste, some of my favourite places are mentioned a few times! Berlin was such an amazing city with so much culture, history and incredible architecture. I left a piece of my heart there. Budapest absolutely stole my heart as well, it was beautiful and so interesting and as lame as this sounds, I loved the vibe. It just had a really good vibe and I never once felt unsafe, loved every second.
There's a few places I've been and expected to not like it, and ended up being surprised. I went to Sibiu, Romania (I didn't choose the destination) and I had such low expectations but it was an amazing city, I thoroughly enjoyed myself and would happily go back (I felt like a millionaire out there, it was so cheap). I also had low expectations of Lanzarote after years of hearing it referred to as Lanzagrotty, just went for a cheap beach break for dc, stayed in Playa Blanca, it was brilliant. There are some very brits abroady spots but if you avoid them there are some brilliant restaurants and the beaches were lovely.
Anyway, on the subject of the thread
Places I didn't like
Cancun - felt dirty and intimidating (highly recommend Riviera Maya though)
Amsterdam - Been 5 times for different reasons, loved it at first, but it's become so over commercialised, over priced and full of lads on stags do. Imo it has lost, or is very fast losing its charm. (Rotterdam has a lot of the charm still, so I go there instead now, I also loved Haarlem!)
NYC - Same reasons others have said really (Boston however I loved!)
Hollywood - Dirty tourist trap
Disneyland Paris - Meh, save your money and go to Disney world
Marrakech - Some areas were a bit grim, but even the bits that could be nice were just full of pushy men trying to sell you knock off gear or put cobras on you, take a photo and empty your bank account to pay for it.