Originally Posted by
Powas
I simply don't care.
Anime is anime. If I like it, it's all that I need, no matter if it's 'mainstream' or not.
^
This.
Though our opinion may differ, personally, I define mainstream as something that is more well known and generally accepted by people in some cases.
Are mainstream anime are true representations of what anime is? No, but it can define an anime fan. For example if Bob likes watching Naruto then he counts as an anime fan. He likes Naruto and it IS an anime, whether it being mainstream or not doesn't really matter.
You can't judge what anime is from one perspective by watching all the mainstream series while dodging the lesser known ones, or vice versa. Although I found it easier for someone to like anime by introducing the mainstream one, it can help giving a bigger picture of what an anime could offer and so it could help people who wants to dig deeper into it.
Of course, there are people who choose the art over storyline, or character development amongst other things, but that's more into personal choice.