Freedom Force vs The Third Reich is, in essence, more Freedom Force. Same engine, same characters, same voice actors, same writing style, same art. It would be more honest to call it a stand-alone expansion, in the vein of Homeworld: Cataclysm, than a true sequel. In fact, the Cataclysm comparison is very pertinent. For not only is Third Reich more Freedom Force, but it's a better, more polished edition.
Like its forefather, Third Reich has the player leading up to four heroes at a time, from a stable of about two dozen to choose from. They have RPG like stats such as Strength and Endurance, as well as power abilities that also increase through the expenditure of character points which are earned through gaining levels. Fortunately, all characters gain levels at the same time and the player is not punished for not bringing a certain character along. This nearly-equal XP gathering also helps keep the game balanced, by not permitting any single character from becoming too powerful.
The characters are very Silver Age. This means that they are the same kind of selfless do-gooders one would expect from a 1940's Superman, but they also have personality quirks, except perhaps for Minuteman - he's just batshit insane patriotic.
As such, the dialogue is suitably cliche. Minuteman is constantly praising justice and America and the loyal servants of the government. Mentor, a brainiac alien, speaks like a brainiac alien - in overly large words and with phrases like "the power of the mind compels you to speak the truth!" Every word is emphasized, every phrase full of exclamations not unlike Robin's "Holy Holiest of Holies" series from the Bat-Man TV series. Objects and vehicles pertaining to Freedom Force are suitably named, like the Freedom Flier, and so on.
Sounds terribly cheesy, doesn't it? Well, it certainly is, but it works. The voice acting is just over-the-top enough to by humorous, though it can get tiresome over extended dialogue scenes. In fact, it's charming enough that what we really mind is when the text or voice acting goes so far beyond the call of duty it seems to mock the idea. There's a fine, subtle line between gently poking fun at old comic books while respecting the spirit, and cynical parody. A few times, it seems like Freedom Force vs The Third Reich steps across that line and it can be a jarring experience. Fortunately, the music is always there to keep the player in the mood - it is very well-suited to the setting and nicely composed. Its timing - to be stirring, scary, or sad as necessary - is excellent.
Suitably enough, the characters and action play out in a Silver Age fashion. Heroes don't kill their foes, they defeat them. Villains, no matter that they tried to start a nuclear war or other horror, will spill their dastardly plans once properly beaten.