"Apples are delicious."
Interesting: is delicious is written 맛있습니다 and its pronunciation is 마싰습니다. The sentence demonstrates a problem common with foreign learners. A hurtle that must be solved to effectively communicate in Korean. Us learners need to pay particular attention as to how conjugation impacts pronunciation.
It might be easier to understand by breaking down the phrases. Each has "있습니다" in common (I think there is a typo in your q?). This means "it has <>" because it stems from the verb "to have" (있다). So it is a matter of learning the differences between "멋" and "맛". Both mean taste but 맛 is about flavour. So the phrases read has... something has tasty/yummy flavour, versus something has 'good taste'.
When it's a general statement, in Korean they use the topic maker of 은/는. It doesn't matter that we would call it the subject in the English sentence.
In Korean, subject makers are usually used when you're speaking about particular examples of the item. Like, 사과가 would usually mean "the apple".