Quality ice cream should generally be smooth and soft. It should melt pleasantly and not too quickly in the mouth. Noticeable ice crystals, sandy texture or coarseness are undesireable. While taste is a very personal matter, flavour purity is considered important by many. Along this line, flavours ought to be both easily identifiable and “natural/pure”, rather than muddled or artificial. Neither should flavours be overly “distorted” in character (fruit flavours being robbed of their freshness because of too much added sugar being a typical example here). It could also be noted that making flavours overwhelmingly strong is generally considered detrimental to a nice tasting experience. You can read more here.