A typically developing 5 year old would usually be able to say the following sounds accurately: m, p, h, w, b, n, f, t, k, g, y, d, j, ch and sh. Now it should be noted that every child develops differently and there is a wide range of what is considered to be within normal limits, however in general, you should be hearing the above sounds in your son's speech. If you do not here these sounds, or they are substituted with other sounds (i.e. he says "tup" for "cup" or "gog" for "dog") then he may have a speech sound disorder. I would suggest talking to your pediatrician and/or seeing a speech language pathologist for a speech screening.
Ali Matisse, MS CCC-SLP