I received a gift of $50,000 from my parents during the marriage. The gift was intended to be to me alone—not to me and my spouse. The $50,000 has remained in an interest-bearing bank account since the time I received it. Is my spouse entitled to half of the value of this gift?

No. This is another example of separate property.  Property acquired by a spouse during marriage by gift is considered separate property.   Unlike marital property, separate property is not subject to equitable distribution.