I'm of the general opinion that subtitles are best used in sequels or other non-primary versions of something, otherwise they tend to lengthen the name unnecessarily.
For some reason, the various Xeno-named games always rub me the wrong way.
I'll try to think of something fun. Right now, my brain is only coming up with silly names like "Earth Immigration Bureau", "Crop Circle Critics", "Soldiers Against Cattle Experiments", "SETI: The Sequel" and "Black Suits".
EDIT: First serious name attempt, "We Are Not Alone", "First Contact", "Final Line of Defense"
I'd have to agree with you on "Xeno-" prefixed names, which is why I didn't even mention that one in the first place. I, too, have had an inexplicable aversion to them, but seeing as how there aren't a lot of good options out there for the taking, Xenocorps at least fits and is unique (for those reasons I'm perhaps leaning a little bit in that direction right now).
The other names you propose still seem to fall into the generic/cheesy/cliche category. For some reason it's quite difficult to come up with something compelling that
isn't ridiculous... Yesterday I posted this on the blog, and while considering different ideas that afternoon, Hot Pink Elephants from Space Ate My Pajamas actually popped into my head... that was definitely a WTF moment (and got me laughing, of course
).
Some of the fun names out there would be nice to go with if I wasn't aiming to give the game a serious theme. I like the idea of Earth Immigration Bureau ("Welcome to Earth! You may die now..."), and I still remember Areyar's "UFO: ASCII Unknown" (although the game won't eventually be ASCII only).
I haven't heard (or thought) of anything that strikes my interest any more than the existing options, but there's still plenty of time to let the news get around and hear more opinions. (I wasn't planning on even bringing this up quite so soon, if not for the unfortunate fact that my original blog post couldn't be published so I wanted to come up with a different topic to fill the void.)