【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.