The Immortals of Terra represents the collision of the niche audience of adventure gamers with the niche audience of Perry Rhodan fans.
Honestly, it's impressive that The Immortals of Terra even got released in English-speaking countries.
The subtitle of The Immortals of Terra is A Perry Rhodan Adventure, which itself provokes a reaction among American gamers of "what?" or "who?". Perry Rhodan, as it turns out, is a science fiction series (Wikipedia says it's a "space opera") originating in Germany, which has produced over 2,000 weekly novellas since it began publishing in 1961. It's very popular, obviously, and pieces of it have been translated into a whole pile of different languages, including English.
The series started by predicting that the first moon landing would happen in 1971 (off by only two years -- not bad, right?), at which point alien technology was found on the moon's surface catapulting humankind into a new age of technology and exploration. Mr. Rhodan himself plays an integral part in this advance, usually playing the part of rugged, reluctant hero figure. If I am to interpret certain parts of the mythology introduced by the game properly, Rhodan (along with, at the very least, some other high-ranking officers and officials in the series' universe) at one point received something called a "cell bath", granting him something like immortality. This convenient little plot device allows Rhodan to far outlive the 20th century, despite the fact that everything begins in 1971.
Now, all of this information was gleaned from some combination of the game itself, Perry Rhodan fansites, and Wikipedia, as I have never myself read a Perry Rhodan book. As it is, there is but a single Perry Rhodan book available new on amazon.com, the first part of a six-part series, the last five parts of which seem to have been forgotten since the first part's release early last year. These are not books that are in the common American lexicon, or even the common American science fiction lexicon. Before that 2007 release, itself looking more and more like an unintentional one-off, there had been no English translations since 2001. The history of the series has seen similarly sporadic attempts at translation, all of them motivated by a love of the series rather than any money-making designs.
Obviously, the Perry Rhodan name itself certainly wasn't enough to prompt an American or British release.
The point-and-click adventure genre has been experiencing something of a renaissance of late with the success of two seasons (and counting) of Telltale's recent episodic take on Steve Purcell's Sam & Max. It's an appeal to simpler days of PC gaming, when every action taken by the player prompted a singular reaction, and if you search for long enough and take enough actions, you'll be rewarded with advancement of the plot (or at least a one-liner, perhaps a little bit of backstory). It's an approach that has reawakened the gaming bug in PC gamers whose interests may have waned in the age of MMOs, first-person shooters, and eight-hour strategy sessions; gamers of an age that just happens to intersect with the ones who would be interested in a 2,000-part space opera of which they can't even read more than 1,900 pieces.
That said, it is a point-and-click adventure game, and sometimes, that's enough to get excited about on its own. There are no glaring flaws in the design, but the game just feels like the victim of a don't-screw-up design mentality. Unfortunately, it's not enough for a game to not fail. It needs to grab the player in some way; it needs to stand out from the pack for some reason other than simply its unusual pedigree. The Immortals of Terra: A Perry Rhodan Adventure never offers a true reason to be invested in the missions at hand, nor in the universe of Perry Rhodan as a whole.
I'm sure that there's a perfectly good reason for the success of the Perry Rhodan series in Germany. Unfortunately, it's going to take more than this game for this particular American to find that reason.