I haven't had a chance to read the full thing yet (I'm not even sure how long the full thing is - it seems like the "read next page" buttons go on forever), but this is really interesting, even though I think the comments sometimes oversimplify things. Then again, it can be hard to fit things into Tweet-sized bites.
If I remember right, I started off with my dad's comics collection (Marvel, DC, DC's Vertigo imprint, a bit of Image Comics) and then discovered manga via my wonderful public library and got completely hooked on that. I now read Japanese manga almost exclusively, for some of the reasons stated by the commenters. I like that, generally, it's easy to know where to start. While there are some authors/artists who create complex worlds and series with lots of crossover (CLAMP and their billions of cameos is the one example I can think of right now), and some authors/artists who "finish" a series and then reboot it or start a related series (Masashi Kishimoto, Nobuhiro Watsuki), and folks with related light novels and whatnot, you can still usually start with volume 1 of whatever they're working on and be fine.
I like that authors and artists don't generally change during a series' run - the consistency is nice (although even a single artist's style can change drastically in a relatively short span of time - good example, Maki Murakami's Gravitation, where the earlier volumes and later volumes look like they were drawn by completely different people but weren't). Now that I no longer live near a good public library with an excellent manga collection, I also really like that you can find lots of series with a definite ending and beginning, and lots of series with an affordable total number of volumes (less than 10 or 12 is my preference, anymore).
I got started with manga back in maybe the late '90s, which I think also made a difference. First, there was Tokyopop and its cheaper volumes. Second, volumes were more likely to include translator and cultural notes back then. Those cultural notes helped a lot.
Oof, so much nostalgia right now. I miss the days when I had good feelings about Tokyopop, and when Del Rey put out volumes of manga with pages and pages of translator's notes. ::sigh::