This got a bad rap, but it's not as bad as you'd expect. Stallone is a strange choice for the lead, but he does OK. The revelation of whodunnit is a let down, though, due to its almost stereotypical predictability.
Don't complain because there isn't much plot, or because a delicate political situation is simplified. When, since First Blood, has a Rambo movie been any different? What you get is an amazing action turn for a man of Sly's vintage, an adrenalin-rush of violence, and none of the comic-book oiled bodies and explosions of parts two and three (well, one ENORMOUS explosion that is so unbelievably over the top, you've got no choice but to applaud it!).
Had the feel of its predecessors but it scores higher on effort than achievement. Simply put, Ford is too old to pull off the role, and aliens was an ill-informed direction to take. It was OK, perhaps as good as can be expected for a third sequel starring a 65-year-old lead. Maybe we've been spoiled by the recent exploits of McClain, Balboa and Rambo.