I think it depends on what you like about languages.  I preferred Russian to French for example, because I prefer languages with harder, more gutteral sounds.   And because I like logical grammar systems, I really like Spanish because all the grammar rules are quite clear and make sense, with few exceptions.  

I think learning a language has no relation with easiness or enjoyment , it has relation with visiting the place or living in the place where that language is spoken.

I think some people enjoy learning some languages more because they might like the culture, or simply the language. But I think some languages are definitely easier for some people, usually depending on what their native language or languages are. It's easier to learn Italian or French when your native language is Spanish, for example, but Russian would probably be more difficult.

I like languages which are very different from my own. Like Japanese or Mandarin. Languages which are very easy for me I get bored of, which I would imagine is the opposite for most people. Though I do like Spanish, because I really like the flow and accent that comes with the language.