I have friends who adore Lee Child's "Jack Reacher" stories: they refuse to watch Tom Cruise in the role as he doesn't capture the essence of the character. If nothing else, Jack Reacher is 6'5", and Tom Cruise is 5'6" - not quite the commanding presence that Reacher is supposed to have. After two movies, I'd say it goes deeper than that: Cruise has created a competent and amazingly non-descript and uninteresting guy.
This time, he's rescuing Major Susan Turner (Cobie Smulders) - very nearly as competent as he is, but nevertheless over her head trying to figure out a series of mysterious killings in the military apparently caused by one of their external contractors. There's also a mildly interesting subplot about a young girl who may or may not be Reacher's illegitimate daughter.
The movie goes for action and tension, and achieves neither - the action is nothing new, and the characters just aren't appealing enough to invest in. They're fine, but the whole thing is too generic to appeal.