Hi, Lexico, how are you? Haven't seen you on MSN for a very long time, and you are still so active here. Glad to see you here again.
Can I say "objection" to this question? Because I don't think we can say one language is more difficult than the other.
Why? Every language has its own depth, depending on what kind of level you want to achieve. If you want to be an expert in the English language, then you have really a lot of thing to learn about the language, and I can guarantee, a normal native English speaker don't know a lot of things, because, all these things are just useless in daily conversation, who will bother to learn it? This apply to other languages as well, say French, if one want to become an expert in this language, then one will have a lot of things to learn too. And learning is a never ending process, how do you know that you know everything? Hence all languages are difficult.
Moreover, why some people find it easier to learn one language, but the other find it a hell time. That depends on various factors, such as the enviroment, the native language that this person speak, the interest of this person, the amount of aid given to him/her etc.
A French will find it easier to learn Spanish than a Chinese, that is because French and Spanish have a lot of similarities. A Chinese will pick up Japanese faster because of the similarities in kanji and certain words. A French will probably has more hard time to learn kanji than a Chinese.
A psychological reason that one must take into account is, quite a number of people will normally think that their own language is most difficult, that is because they are more "proficient" or more "expert" in their own languages than other languages they acquired, but at the same time may know very little about their own language, because they know very little about their own language, the find that they have so much more to learn about their own language, hence find it difficult. On the other hand, these people who acquired other languages find these languages "easier" is because they are not bothered to become an expert in this language, lacking the knowledge of all these languages, hence, giving them an illusion that these languages are easier. When one try to learn another language from a language that one is most used to, this person will inadventently relearn or rediscover his own language, thus, giving him an illusion that he don't know so much thing.
Of course, some may not think this way, some may think that one language is more difficult than other after he/she learnt it. But there is psychological reason to this also. Thinking that one language is more difficult than the other just because he/she find it difficult to understand or always tend to make mistake in this language doesn't make this language instrinsically difficult. It is this person ability of understanding. Again, one will argue that, what if a lot of native speakers make the same mistakes too. But one has to rethink on what is the purpose of a language? The main purpose of language is to facilitate communication, we don't decide how a grammar supposed to be, rather, the structure of the grammar will follow the trend of the speakers, if everyone has been speaking in a certain gramatically wrong way, because everyone has been speaking like this, hence this gramatically wrong way is the correct way, and the gramatically correct way is not really correct, since the majority people do not want to use it. Why we want to force ourself into accepting certain theories that we may not use in daily life, just because people previously using this language say that this is the rule? Why can't people who are using the language currently decide the rules?
Some people say that French is more difficult than English, one reason is because of the conjugation of verbs. If you have been conjugating verb everyday, will you find it difficult? You may not be able to conjugate every words, because no one can learn every single word in his own language, those exception in conjugation don't make the language difficult, it all depends on how used you are at it. Therefore saying that French is harder than English is not true, English does have exceptional grammars too!!! English has more vocabulary to learn than French. So how are we going to compare which is more difficult? Both languages just have its own uniqueness.
Then again, some will say English is relatively easier than Chinese. Is this true? To a lot of Chinese people, English is a hell to them and Chinese language is a breeze to them. To an Englishman, chinese language will then be a hell to them, first they are not used to the tonal pronunciation, second, they will have to spent a lot of time memorizing 2000-3000 kanji, and this is definitely not an easy task. Even tough, English may not have those kanji or tonal thing, English has more vocabulary than Chinese. Which may make it more difficult? How are you going to judge? If you want to be an expert in English, then you have to study old English, so a lot of people will say that old English is extremely difficult. Other the other hand, if you want to be an expert in Chinese langauge, then you have to study archaic chinese too. That is very difficult too. Hence, how are we going to compare the difficultness of these two languages?
All in all, I really don't think we can compare languages. Just like we can't say physics is harder than economy or vice versa. The more proficient you want to be at a language, the more difficult you find it. Because if you really want to know more things, you may go into a situation that make you feel you don't know so much.
Food for thought:
A person can command 100 languages, but do not produce any good work. A person who know only 1 language, and this person produces works that set the general trend for the language. What do you think?