You know what be a great movie to see from the aliens' perspective? Signs!
Can you imagine the briefing for this mission?
Commander: "All right troops! It's time to invade the Earth!"
Troops: "Yeah! Can't wait to zap them!"
"Just be careful. This is the acid world. Every liquid on the planet is laced with acid. It rains acid. The natives spit and bleed acid. At night, acid condenses out of the air itself. "
"We got protective gear, right?"
"Uh, no."
"But, at least we can shoot them, right?"
"Our new doctrine is to subdue the planet through martial arts alone."
"Well, we can do that. There can't be more than a few thousand of them and it's not like they have weapons or anyth-"
"Six billion. And you can expect every population center to be awash in firearms."
"....We're all going to die, aren't we?"