The original Ben 10 series was a show about a kid who goes on a road trip across America with his eccentric relatives, and sees all the weirdest parts of Americana along the way.
It had aliens, cryptids, mad scientists, classic movie monsters, people with mutant powers, voodoo sorcerers, and the illuminati.
Alien Force has aliens. It's a show about a guy who turns into aliens to fight aliens, and everything in the series that you thought wasn't aliens is actually aliens all along.
Basically, the original series you a unique setting full of interesting things that made you wonder what else could be out there, and then Alien Force gave you the most disappointing answer imaginable. Aliens, that's what's out there. Nothing else.