Wow, awesome, wonderful, and the like are good expressions and indeed they denote that you are happy because the event is happy. But I just came across a weird situation!
In India, medical students, when pass their finals, are placed for the internship where they learn things from their seniors. The purpose of such an internship is to learn newer things that they might have missed in their previous academic years.
Heart murmur is one of the abnormal heart sounds and we medical students seldom find such cases. Now, imagine that the senior got a patient with such 'murmur,' and he then asks the fresher to hear it because the fresher hasn't heard it ever. Here comes the question of expression!
Dr Anderson, senior doctor, after examining the patient : Ah, a clear case of heart valve defect; Dr Jackson, you should listen to this.
Dr Jackson, a fresher who has never heard that before : (EXPRESSION??????)
No word fits there! The event is not happy. He cannot utter wow, amazing, awesome, super... The patient is alive, listening to his utterance. The doctor wants to express something exclamatory but which word then? 'Damn, holy s**, nothing will work!