When Bruce Willis was asked to cameo in The Expendables, he must have had a hard time keeping a straight face. Because at that point he must have known that he was already involved in a movie that was doing everything So Very Right where Stallone was doing it So Very Wrong.
So, Bruce plays Paul Moses, CIA Blackops Badass (retired). He's retired to suburban Ohio, and basically lives out his days flirting over the phone with the girl who manages his pension (Mary Louise Parker). Unfortunately for him, something he did many years ago has suddenly become relevant again, and a hit squad is sent to his house to kill him. This does not go well for them.
Realising he is marked for death, and figuring that they may use his relationship with Mary Louise Parker against him, he rolls up to her place, and kidnaps her, and goes on the run. Eventually, she is convinced that he's not actually just a crazy stalker, and people are actually after her, so the two team up to work out who's doing this, and why. On the way they collect a band of ex-spooks who Bruce used to work with, including Morgan Freeman as Morgan Freeman, John Malkovich as a comedy version of they guy he played in In The Line of Fire, and Helen Mirren as MI6's top sniper. (Many reviews have stated that Helen Mirren With A Sniper Rifle is reason enough to see this film. I cannot disagree.) Also in the mix are Brian Cox as a Russian Agent of Bruce's acquaintance, Richard Dreyfuss as a dodgy arms dealer and Karl Urban as the CIA's current best Blackops Badass, assigned to clean up the situation.
Now, if you look at the above list, you'll see they have one thing in common; actors who aren't necessarily primarily known for comedy, but who have great comic timing. And that's what the film's like. It's not primarily a comedy, it's an action movie, but while it's not dishing out the thrills, spills and explosions, there's plenty of highly amusing interplay. There's not a bit of it where there's not something happening to entertain you. I want to particularly namecheck Karl Urban on that, since it's a bit lower key for him. He basically spends the whole film, one misstep or misdirection behind Bruce, and there's a kind of quiet pained slapstick to him.
Downsides? Well, it's not Ibsen. If you've read the original graphic novel, you'll notice that the themes involving the morality of covert operations are completely absent. In the book, Paul Moses is a man tortured by the memory of the terrible, terrible things that he did for his country, and who has been targeted for death as much as anything because the newly appointed head of the CIA has learned what he did, and can't bear to let him live unpunished. And in adaptation, Moses has gone from being a horror of the cold war era who killed thousands, perhaps even both JFK and Martin Luther King, to being this sweet cuddly guy who killed terrorists, destabilised rogue states, and basically seemed to have done only Good Deeds. In fact, we're presented with four main characters who are blackops operatives with hardly a stain on their characters. So you know we're firmly in fantasy land here.
Still, with that said, and understanding that there is no objective in this film but to amuse and entertain, this is two hours of highly amusing entertainment.