Samaritan is a by the numbers action flick but that's not necessarily a bad thing. 
One of the key problems with a lot of modern movie making, is the constant need to experiment and at times, inject social messages into what it supposed to be entertainment. 
Samaritan follows a well known and well worn, by the numbers, action film formula. It tries to throw in a twist I saw coming pretty early on but that's alright. In essence, this film is inherently watchable. Stallone still has excellent screen presence and the chemistry, between him and the young boy, works well.
My advice, ignore the carping from the soy latte class of movie goers who bemoan a lack of sophistication. Its often the simple things in life that are most enjoyable and this is one of them. 
In summary, Samaritan wont win any accolades for high brow cinema but what it does, it does competently enough to be reasonably enjoyable and entertaining. For many of us, tired of shallow cinema sophistry and intellectual pretension, that's what really matters.