I think that Ephron's film can be seen as a Romantic Comedy. There are a couple of reasons whySleeplessinSeattlewould fit into this genre. The first would be the idea of being able to blend the drama of romantic love between two people with the element of comedy. The film features both, in large part due to Ephron's script and envisioning. Consider a basic definition of the genre:
In a typical romantic comedy the two lovers tend to be young, likable, and apparently meant for each other, yet they are kept apart by some complicating circumstance (e.g., class differences, parental interference; a previous girlfriend or boyfriend) until, surmounting all obstacles, they are finally wed. A wedding-bells, fairy-tale-style happy ending is practically mandatory.
Sleepless in Seattleaddresses all of these major points. The Tom Hanks and Meg Ryan characters are extremely likable, being evident to all that these two are meant to be together. The geographic element as well as the notion of fate and destiny play with both of them and us in keeping them apart and eventually bringing them together. The ending to the film is one that indicates that unity and harmony is evident with their union, something that is part of the genre. There is little evidence to indicate that they will divorce, separate due to adultery, or realize that the other one has been leading a duplicitous life and thereby ending the relationship. Rather, when they are together at the end, it is almost a "mandatory" element indicating that they are to be together, helping to affirm the conventional, and sometimes mythical, qualities of love. In this, the film fits the notion of a Romantic Comedy.