I'm not wild about 'Precursor Civilization' themes in science fiction, though I've enjoyed a number of settings that use this notion. One advantage of it, though, is that it give you an explanation for having a bunch of races roughly analogous to humans -- the precursors seeded it all. Plus, it gives you an excuse to bring in stuff Indistinguishable from Magic in the form of Alien Artifacts. These become plot devices in themselves.
Anthropomorphism makes for much more straightforward roleplaying and significantly reduces your FX budget for TV shows. Personally, I prefer to have aliens that couldn't be mocked up using just some prosthetic ridges on the face. I can see why they're practical to use. But I like for a setting to have some proportion of its regularly occurring alien population sufficiently inhuman that if they were on a TV show, you need puppetry or computer animation to represent them. I think Helios Rising has that much covered.
Roleplaying an alien mindset is a sufficient challenge, especially when the best the game designer can hope to do is give you a broad stereotype, since it's difficult to immerse you in the alien culture. You then individualize that stereotype, but do so out of your human experience of individuality. I can see how roleplaying may be a chance to attempt to put yourself in a truly alien mindset, but I think that a game that would be ideal for that has not been invented. The roleplaying games we play are about using a set of abilities and imagination to overcome challenges in a manner consistent with a character. Dealing with totally alien mindsets derived from totally alien physiology would demand a fairly different kind of game.