I saw Steven Spielberg's War of the Worlds, and thought it was okay. It made me wonder, though, whether creatures from another planet might really be able to be killed by Earth germs? Well, could they?
What a weird question! Of course aliens could be killed by Earth germs, just like they could be killed by Earth bullets and Earth tigers. And if you saw Independence Day, you know that their computers would be vulnerable to our computer viruses. Their appliances would likely not, however, be compatible with our electrical system without an adapter, though.
Speaking of the movie, I think it's kind of interesting which elements of the original novel Spielberg chose to keep and which he discarded. Having the "Martians" already be on earth was, in my opinion, completely dumb. Why not have them buried on Mars instead of Earth? That would avoid a lot of problems.
It was also neat that he made the Martians much more bloodthirsty than they were in the previous film version. Again, much more like the book.
Those familiar with the story will also likely be surprised by the extra twist at the ending (a Martian bacteria wiping out all life on Earth). It's amazing what lengths the studio went to to keep this from being leaked in the press.