You might find it useful to specify what you mean by "commercial fiction" and "literary fiction". I note that in the tags you placed the word themes, perhaps indicating that you want to know if the themes of the story are worthy enough to warrant it a work of literature. Certainly all of Graham Greene's work is literary rather than commercial in that they are off great calibre and literary quality, if that is how you are choosing to define the words.
There are a number of literary qualities that could be cited to support my claim, but I will content myself with merely focussing on one of the themes in the story which focuses on the hollowness and rottenness in both the setting, the lives of the characters and in the society at large. Consider how the setting adds to this bleak atmosphere - the story occurs in an "impromptu car park" where the first blitz occurred where the boys meet. Their lives and their play is dominated by images of destruction and waste. The name of "Wormsley Common" itself gives rise to images of rottenness and emptiness, and this gives rise to the main protagonist of the story, T., who shows himself to be empty at heart - he is so dangerously detached from any form of emotion that he is a complete nihilist due to the hollowness of his life and his world. Consider his words:
"All this hate and love," he said, "it's soft, it's hooey. There's only things, Blackie..."
In the characterisation of T., Greene achieves a truly incredible feat by accurately depicting a child who is hollow at the core and heartless. All of these qualities serve to demonstrate that this is a masterful work of fiction which cannot be defined as "commercial".