The animated series Ben 10 started running on Cartoon Network way back in 2005, now 15 years ago. The series was immensely popular, so much so that it was revamped after it ended...four different times.
That's right, in total, there have been five iterations of the show that originally aired simply as Ben 10, a series about a 10-year-old boy who, while on vacation with his uncle and cousin, found an alien watch that gave him the ability to transform into any of 10 aliens, a power he uses to become a sort of superhero. The most recent variation was a total reboot of the original series, (set in a different timeline) in 2016. The other three, Alien Force, Ultimate Alien, and Omniverse all take place when Ben is 15 or 16.
Though many remember the original Ben 10 with the most fondness, it's probably Ben 10: Alien Force that deserves the most credit for style, world building, character, and story. The original series may have introduced these well-beloved characters, but Alien Force (along with Ultimate Alien, which was more or less the same series with a different name) made the world what it is after its premiere in 2008, and deserves more props for all the innovation put into it, for at least three major reasons.
The Animation Style
Firstly, the animation style in Alien Force is a definite departure from the style used in the original Ben 10. Though both series still used the same highly-detailed, hand-drawn frames that cartoons have gotten away from in recent years, the style used in Alien Force was much closer to realism than the more stylized animation in Ben 10. This isn't to say that stylized animation is any less skillful, but it does definitely take a lot more time and attention to detail to make it look good.
The more serious, somewhat gritty tone of the show is thus taken more seriously. The shows that looked most like it in public memory at the time were Avatar: The Last Airbender and Teen Titans, both shows with huge, dedicated fanbases and detailed, well-crafted plots.
The High-Stakes Storylines
Not only was the animation more involved, fleshed-out, and dark: So were the storylines. They weren't signaling similarities to Teen Titans and Avatar for viewership: They had the storytelling, plots, and character development to back it up. Alien Force almost completely changed the genre of the show. It wasn't just a kid's superhero cartoon with a lesson at the end anymore; now it was an involved sci-fi drama that dealt with more mature themes in its conflicts — resulting in much higher stakes for the heroes.
The missions the so called 'Alien Force' must face endanger their lives and their city far more often than the ones they saw while vacationing with their grandpa, placing a more direct responsibility on their shoulders to be heroes. This, in turn, allows the show to deal with much darker, richer content than its predecessor.
These higher stakes are introduced right in the very first episode of the series, when Grandpa Max turns up missing from his trailer. Over the course of their mission to find him, the characters come to understand the world they live in much better than they were when they were children. Now that they are older, they are more able to understand the secrets of the world they live in: Secrets like the plumbers, the secret force of space investigators that their grandfather was a part of. Their advanced understanding allows the fascinating, intricate world they live in to be built out much more, in the classic comic book style that fans can really sink their teeth into.
In addition, the characters in the show being older allows their characters to become much more developed and interesting. Ben is no longer just some annoying, over-confident kid: He's a hero with a complicated relationship to his omnitrix, and a teenager with issues talking to girls. And Gwen isn't just the bratty, tattle-tale goody-goody cousin: She's a smart, confident young woman with her own alien powers, inherited from her grandmother, and her own storylines (rather than just an occasional episode devoted to her).
Something for Everyone
That brings us to the last and best thing about Ben 10: Alien Force: The diversity of story. The original Ben 10 was a TV show aimed at young boys, that couldn't really hold the attention of older audiences, and did very little to cater to any female viewers. This show fixed that problem in a couple of different ways.
First, they added more main characters, and split the focus between them more evenly. They gave Gwen more time, and more power, and had her explore her own story arcs in the development of that power, giving girls someone they could relate to who had more presence in the show. They also added Kevin Levin, a former villain, as a third member of the trio, to play the team's bad boy, and a love interest for Gwen.
That's another way this show deviated from its previous iteration: In Ben 10, there weren't many personal, non-action storylines, and the ones that were there didn't carry much weight in the series. In Alien Force, the personal stories not only matter almost just as much as the action stories in terms of plot, the two often intersect. These more relatable plots work much better for older audiences — especially the slow burn romance between Gwen and Kevin. The more even balance between character drama and alien action and intrigue made for a more rounded show overall.
Altogether, the more realist sci-fi style, and more balanced, high-stakes, dramatic writing for Alien Force (and, by extension, Ultimate Alien) far outpaces any of the other cartoons in the series in terms of quality. It's often overshadowed by the original because of nostalgia, but make no mistake: It was one of the best television shows of its time, and if you were a fan of any Ben 10 series and haven't watched it yet, you absolutely should.
And, good news: According to one of the creators, if the reboot of Ben 10 continues and keeps doing well, we might see the events of the show naturally segue into a reboot of Alien Force too!