Sounds pretty normal to me. When my daughter is in the mood to do something she does it for hours, but at other times she will only spend a few minutes on each thing. In my daughter's case there are times where she will spend all day doing one thing whether it's playing in the sand, with blocks, painting, "writing letters", playing with her stuffed animals, etc., BUT she has to initiate and do it on her own. When I try to do it with her or suggest what to play with, she'll only spend a little time playing and then move on to something else.
I'd say give him a variety of things to do, but let him direct his play and enjoy it. (A craft corner that's always set up may encourage him to do more creative play. Make a small table where things like coloring or playdough are already prepared, so he can go and do it whenever he likes.)