Trying to copy X-Com is, in theory, easy. Turn-based combat with a square grid mixed with  base management. It's not even to say the original was perfect: it had some serious game-breaking ones and was very imbalanced if you knew what to research.

Still, no game managed to do it right, not even their creators. The closest one is Terror from the Deep which is basically a reskin of the original with a water theme and, ramped up difficult by nerfing most of the good original weapons and very, very large maps.

So I watched the gameplay video with skepticism and found me surprised. The gameplay look not only good, but improved. The small details like the takedowns and the memorial show a level of polish I did not expect and make me think maybe this game maybe been on production for a while instead of being a rushed down project.

tl;dr Gameplay video made me pre-order Xcom.

p.s. And about Xenonauts, it looks good in theory (like most X-Com clones do)  but Xcom have a release date.