Simple and entertaining.
Some call it a "guilty pleasure", and yes, it is. At times, characters and acting are like those movies you made with friends at high-school or as freshman (you did, didn't you?). A bit cardboard, but friendly fun, and over-the-top.
Well, this has a bit more budget, and Arnie in it (plus a cast of Peter Stormare, Luis Guzman, and a handful of other solid actors). But at heart, it's a simple shoot-em-up action movie; no complexity, no surprising twists. What will happen is obvious from the start, as if this was JACK SLATER VIII; how it will happen is what you get to watch.
Don't expect much, just enjoy it.