I thought it was pretty good. I didn't go in expecting an amazing plot, but it kept me entertained throughout the whole thing. And yes, some bits seemed incredibly cliche.
I'm not too concerned about the back story of the aliens, since, we mainly follow that group of marines through the entire movie, and is more like a 3rd person limited perspective. We are given some reason's possibly why they are there in the news clips, but that's about it, they never really communicate with the aliens and the aliens didn't seem so interested in reasoning either.
I gave it a 7/10. It reminds me a lot of Independence Day though (although maybe not as over the top and silly). Even down to the "we found their weakness, relay it to all other countries".