Pleasant, pleasing, agreeable, grateful, gratifying, welcome are comparable when they mean highly acceptable to or delighting the mind or the senses.
Pleasant and pleasing are often indistinguishable; however, pleasant usually imputes a quality to the object to which it is applied, and pleasing suggests merely the effect of the object upon one.
Agreeable implies harmony with one’s tastes or likings.
Grateful carries the implications of both pleasing and agreeable; in addition it stresses the satisfaction or relief afforded the senses or, somewhat less often, the mind.
Gratifying is applied chiefly to what affords mental pleasure to the individual by satisfying his desires, hopes, conscience, or vanity.
Welcome even more than pleasing stresses the pleasure or satisfaction given by the thing to which it is applied; it often suggests prior need or an answer to one’s longings.