If you take the original Ghostbusters movie and overlay the basic plot elements with this episode (good vs. evil), and then mix in the Ghostbusters vs. Gozer (Marie vs.Gamble), and instead of a burning, giant marshmellow man, you just have a quick, easy battle that's over in a matter of moments, then, essentially you have this episode (in a nutshell). Sheesh!
I give this sequel episode a 2/5. As for the entire season, a 3/5. If they hadn't shot "Terraium" in both feet, I might be tempted to give the season a slightly higher rating, but that wasn't the case...