I personally think that people who are somehow interested in philosophy (and science of course , especially theoretical informatics , maybe physics to a lesser extent) will enjoy this anime because the two main subjects that have been raised in this anime are some of the most discussed subject in philosophy : - The existence of the "self" and the existence of "God"
That's why i put a 10 foreverything ,but , you might like or not S.E.Lain , but if you not it will not be caused by the fact that it would be a "Bad" anime , but more because he is a complexe one . And most peoples need to understand that beyond our comprehension ( or incomprehension) of this anime , the fact that he is an outstanding anime is that he actually make us think about the developed themes .