American graphic novels have color and, generally, better art work
A lot of popular mangas come out once a month and drag on for years
Is fewer words really a plus? Humans have the power of speech for a reason
The anime made from manga follow the same plot, so it's the same.
Fillers no, pointless subplots, plenty

Manga is popular for the same reason that american comics are popular ^.^

Fewer words than a novel, but lots more dialogue good for if you don't wanna sit down and watch an anime on your computer, or you're bored in a place in which you can't bring out a computer or laptop (like a restaurant)

i don't find american graphics that amazing, colour doesn't make everything better
i know manga can drag on for years but reading a manga compared to watching the anime can be way faster
for people who dislike reading novels or long text manga can be simple and relaxing
anime made from manga usually follow the same plot but ones like naruto has many fillers in the anime so its slower
filler and pointless subplots are pretty similar

anime usually have fillers which most of the time are quite disappointing, especially in the long shounen ones. manga on the other hand sticks to the plot and you can follow the story at your own pace, which sometimes helps in better understanding of the action sequences. on top of that, you could admire the art and actually appreciate the amount of effort the author has put into the work. not to mention, sometimes your imagination of the characters turns out to be far superior than the official ones.

It is all a matter of opinion.

One could be better in the mind of you from someone else. Both are quite popular, laziness, art, character development, depth, etc. The list can go on for ages, but that is of course in regards to anime based off manga or have manga counterparts. Some anime are stand alone projects which were or remain only as anime therefore there can be no comparison. By now, most people should be familiar with my fondness for Eureka Seven which was an anime before it was a manga.
It is one of the few times I can say the anime kicks the crap out of the manga hardcore. Most people grow attached to the original works of a mangaka and though they enjoy the anime adaptation, there are missing things. Many studios create lots of fillers to buy time to animate the canon material and buy time for the manga to get ahead. Some are not meant to be doppelgangers, but tributes to the manga. Someone already mentioned the difference between Miura's Berserk and the anime adaptations.

Miura is a weird duck in the field of mangaka since he has not staff. He does everything by himself creating extremely detailed art and he sure cakes on the blood, gore, and sexual content. You are not going to find this level of craziness in the anime adaptations of Berserk at least not to Miura's degree. Anime adaptations sometimes drag on due to fillers or simply rush/skip over canon material which pisses people off. This removes some vital character development and the plots often times diverge completely.
Some things look better in motion and other times anime adaptations don't stay true to the original work and lose valuable assets that appealed to fans of these works. By having multiple mediums, it sometimes creates parallel universes where characters act differently and change things depending largely on how involved the original mangaka is. People hate change or feel the anime counterparts don't due the manga justice. That is the gist of it anyway.

I like both mediums and sometimes they do clash. There are anime adaptations I despise and anime adaptations I felt surpassed the original. There are some that are equal to each other in quality and some that fall miserably short of their counterparts. You just need to distinguish anime adaptations from original anime works, otherwise confusion results and misconceptions spawn.

manga is interesting. just like the novel....
also, the pictures, and plots, also attractive me..
such as naruto manga and one piece manga.

Good art, good plot, likable characters.

And the nostalgic feeling when you pick up something from a long time ago.

because mother of anime

Because humans exist.............

Manga is fun. Most people don't like reading books with only words, or if they do they dont want to do it for 500+ pages. Manga is popular because it has pictures. But the pictures alone aren't enough. They are moving pictures. It's different than comics, because comics to me don't move, they just go frame by frame. With manga I can pretty much create my own flow and im sure many other people do that as well. Also the stories for the most part are pretty good, and a good story with pictures that we dont have to over analyze will always be popular

Manga is to Anime as Books are to Movies.

But I think the anime is more popular than manga. well, sometimes, it just like the novel, why is novel so popular, many people think it is good.

because it has moments like this

Usually i only read the manga after watching the anime, cuz its faster and most of the time its so much better ^^

Generally im annoyed with animes that leave out parts that are in the manga which is one of the main reasons i began reading them, in other cases its cuz it still keeps going while the anime stops with a halfassed ending.

But if i had to choose, any day i'd pick reading manga over watching the anime (I've yet still to watch the original FMA after i dropped it after 15~episodes, but i've read the entire manga and it was awesome)

Other times like in ongoing shows its more cuz i wanna know more of the story ^^' (Patience is hard when you have a good story infront of you :D)

Why is manga so popular, because its sexy, case closed.