Emotion, like humor, benefits from being drawn out. This is especially true if it's some long-sought moment. You'll wring more emotion if you take a bit of time to set up the moment, and then find a subtle way to postpone it JUST FOR A BIT. (Multiple postponements could lead to melodrama, about which read Theresa's great Cheating Melodrama post.)
An example of postponing the emotional payoff moment is early in Grapes of Wrath. Tom Joad has just been paroled from prison and has walked and hitchhiked home. There's a long set-up of Tom and his friend Casy finding that his home area has been devastated, with evil bankers foreclosing on farms and bulldozing homes. He gets the low-down from Muley, an old man driven into hiding by the bankers. Tom understandably starts to worry that his own family has been affected, and Muley warns him that the Joads are heading to California to find work. So Tom approaches the home in anxiety, and is beyond relieved to see his father (who, fatherlike, quickly assumes he's busted out of jail and is ready to be upset). Tom, above all, wants to see his beloved mother, and has to be warned off running into the house and startling her.
So it's established that he's anxious about their fate, and that they were about to leave for CA and he was lucky to find them. And he's seen his father. So already, expectation is high, and the suspense is like a knot in our throats.
But Steinbeck doesn't give us a quick emotional jolt of Ma seeing him and shouting with joy. No, Pa calls out to her that there are two hobos here, and can they stay for supper. Easily she says yes, as she brings the food out to set on the table. NOT LOOKING UP. Tom can barely restrain himself as his father calls him "Mister" rather than his name, and Steinbeck even draws it out a bit more, having Tom stand in such a way that his mother can't see him against the sun. Tom's mental description of her stretches the suspense out for another paragraph or two.
Finally, though, Tom steps forward and Ma sees him and cries out, and their embrace is that much more powerfully emotional because of the suspended set-up.
Notice that done poorly, this can dissolve into sentimentality or frustration or melodrama. Effects like this are all in the execution. If you do it well, you've given the reader an intense experience. If you do it poorly, you can annoy or amuse the reader. What Theresa and I are saying is-- it's not the event that makes a scene melodramatic or irritating. It's how it's DONE that makes the difference.
And good writers can learn how to design a scene where the event becomes important and meaningful because of how it's presented. Never settle for just putting the event (Tom's return to Ma) there and thinking that's enough, or, conversely, shoving in more emotion than is there naturally.
So what's a scene you've been working on? And how have you designed the scene so that it's more powerful but not too over-the-top?