Shall we start with the bad stuff? Jonah Hex makes very little sense. It feels like there are vast sections of film lying on a cutting room floor somewhere. The DC Comic character's special ability – a brush with death means he can talk to corpses – is barely explained (in the inevitable opening montage) and barely used. The plot, the bit you can make out anyway, is a wholly unoriginal revenge story.
The good stuff? None of the above really matters. Jonah Hex is a three star movie (and I'm probably being generous) but, as bits of fluff go, it delivers. People run around blowing shit up. Megan Fox wears a corset. That's pretty much it but, frankly, for my teenage self (and, occasionally, my middle-aged self) that's really not a complaint. Jonah Hex (Brolin) was a soldier in the Civil War until he drew the line at the barbaric crimes committed by his senior officer Quentin Turnbull (Malkovich). As an act of revenge, Turnbull killed Hex's wife and child and branded his face. After being rescued by Native Americans, Hex found himself straddling the world of the living and the dead, a "gift" that means he's a tracker without peer, a bounty hunter you just can't hide from.
With an ever increasing bounty on his own head, Hex receives an offer from the US Military (in the slightly unlikely shape of Quinn and the highly unlikely shape of Arnett): stop Turnbull and receive a full pardon. Driven by revenge, Hex (with the assistance of his whore-with-a-heart-of-gold lover Lilah (Fox)) steps in to foil Turnbull's plans. These, in true megalomaniac style, involve holding the country to ransom with the threat of a huge superweapon. No, you're right, there's barely an original idea to be had. However, Brolin, Fox, Malkovich, Fassbender (as Turnbull's sidekick) are all fine, the set pieces (while apparently edited to remove violent excesses) are enjoyable and the whole thing skips along in just over an hour, plus end credits. There's also a nice tongue-in-cheek Southern joke with the casting of Tom "Dukes of Hazard" Wopat as an ageing colonel.
Whether the running time makes a trip to a full price West End cinema worthwhile is certainly an issue to debate. It's not big, it's not clever and yes, you'll probably do better to wait for the DVD, but it shamelessly/mindlessly presses the right, if juvenile, buttons.