There are good points and bad points. For example, Frontier is right when it comes to certain characters. For example, if only Lee and Kirby ever wrote X-Men, it wouldn't have amounted to much of anything. Also, lets remember that American comics were given very little respect early on. They were simple work-for-hire for artists. So, they weren't thinking much about stuff like world-building and deepening the canon. While manga's been a pretty big deal art form for a long while. At least since the days of Osamu Tezuka.
I just get tired of the constant "treadmill" of American comics. The constant running to keep up with it. The idea that you're not a real fan of something if you don't constantly read it. The idea that American comics characters aren't worthwhile if they're only published for a small period of time (take Marvel's Sentry for example, which people loved as a miniseries but hated as anything else.