The other day I found the image below on a website and was amazed by its claims on so many different levels!
I will skip over the claims of numbers of hours for proficiency... What kind of proficiency are we talking about? Listening to your neighbour talking about his shopping dilemma or listening to a politician's speech on the radio? Anyway, that is a whole different article in itself...
I have always been a little puzzled by people claiming some languages are harder to learn than others. Sure, some languages' sounds are different from the ones we may know, some grammar systems may be completely alien to what we are accustomed to and some writing systems may puzzle us. But in the end it is all relative to what our native language is and what our personal motivations are.
There are numerous articles online about what the easiest or most difficult language is. I have listed a few interesting ones here:
Personally, I don't think a language can be called 'hard to learn'. I think it is more or less different from the one(s) we know. Learning Spanish if you are a Portuguese native speaker appears 'easy' because the two languages are similar in many ways. Often Portuguese native speakers can understand Spanish speakers and get by in a Spanish-speaking country without instruction.
Secondly, personal motivation is key. If you are motivated learning another language is easier whatever that language may be. If your lovely new husband is Korean and your are American, you are still going to learn Korean to speak to your mother-in-law!