I really think they could do more with this series...
Basic story for eight year old boys. A bit complex, which makes it mildly interesting. Each episode really has its own plot, making it easier for younger kids to understand. But I wish they had made this for older kids, like in the 10-12 range instead of 6-10. They threw in a little romance, but not much.
Let me put it this way. I can compare it to Naruto, an anime rated PG that shows later at night, aimed at kids 12+. Violence: Ben 10 has little realistic violence, no blood. They hit each other. That's about it. Naruto: People are constantly stabbing each other, with sharp, pointy things. There is blood. People get impaled. Sexuality: Ben 10: None. Naruto: The words "pervert" and "sexy" are used frequently. One older man is always spying on women. Womens' cleavage is often displayed in revealing outfits. Romance: Ben 10: Little. It is implied that two characters like each other, but that's it. Naruto: Romance is usually a humorous point. But some characters deeply love each other, and there is some serious kissing. Plot: A boy has to save the world, pretty much with only a few other kids. You know that good will win, it's for eight year olds. Naruto: A boy has a demon sealed inside of him, and people at first discriminate him because of that. The plot deals with more real topics, like war and human nature.
See my point? They could add more romance and more realistic themes and violence into Ben 10 and it would still be rated PG. They could also take out the corny lines. All they need to do is be more realistic. That being said, it is still a pretty good show for young boys. But older kids beware. Anime is much better suited to those 11 and up.