which language do you think is easiest to learn and why?

I can't really say anything about english as it's my primary language. Out of the ones I've attempted to learn, I found spanish was one the easiest, though I'm still far from fluent. What made it easier to learn was probably that it's not that difficult to pronounce or read the words. When I attempted to learn japanese it was extremely difficult for me to pronounce or read any of the words.

It depends on which language you're coming from. For example, if you speak one Romance language, learning any of the others really isn't that hard. Spanish speakers can even sometimes communicate with Italian and Portuguese speakers easily and vice versa.

English is not the easiest to learn, but what can you expect from a language that was essentially created as a byproduct of this? :P

EDIT:

Stupid picture doesn't show up for some reason... Here's the link if you're so inclined: Link

English is the hardest to learn (unless of course you are born to it) but even then it is a problem, if you are into something like Manga or the Samarai or even Karate, then Japanese would come to you, easy, ahh no, but you would get it through diligence, it depends on what you love or are able to handle, I was into Full-contact Karate for years (used to teach the women & kids, but I am too old now) Japanese came to me over time (and a lot of errors), having an instructor who spoke fluent Japanese with a Scottish accent was a pain, but he was a good guy, also learnt a few others over the years, I found it fun, but it was never easy, my young daughter on the other hand, she took to Japanese like she was born to it, she liked Spanish as well, but Japanese was her love, English came easy as well, so we are all different, you just need to find what you enjoy and go with the flow

I would say Spanish and Italian. If you know Spanish, it's an easier transition to learn Italian because they're similar (in some sorts), and vice versa.

All languages are equally easy to learn, by definition! Otherwise they wouldn't exist! What makes them hard is our growing resistance to the acceptance of this idea and the increasing inflexibility of our brains with age. Instead of the simple pleasure we used to have in just making noises that people understood we now see 'learning' as a chore and an obstacle. Nevertheless, plunged into a place where nobody speaks English (not that there are many left) and you'd be amazed at how quickly you become accustomed to speaking (and even thinking) in the local tongue!

As for me enlish language is easiest to use, that is why it's an international language.

English, and that is because it must be else why is it the most popular language?

I would go for Java or sheet music. Don't matter where you can, anyone can learn these languages in a short period of time and can communicate perfectly.