I think you miss one more option.
* very easy
* easy
* average
* hard
* very hard
* fun
But I voted for average, for we haven't got
fun in the choices yet. Learning English I think depends on the learner on how you view the language and on how far you would want to go deeper with the language. The deeper you go the harder it gets. But to sum it all up, I would say it's fun learning English.