Final answer:
The speaker is saying that all other pleasures are mere fantasies compared to a certain authentic pleasure.
Step-by-step explanation:
When the speaker declares, "but this all pleasures fancies be," he suggests that apart from this particular pleasure, all other pleasures are mere fantasies or substitutes for the true experience of pleasure. Therefore, the correct interpretation of this phrase is option C: except for this pleasure, all pleasures are just fantasies of, or substitutes for, real pleasures. This conveys a sense that the speaker may find most pleasures to be illusions or lacking in depth compared to a certain exceptional or authentic pleasure that they have experienced or are referring to.