I want to up this thread.
Recently, I love crowd energy, singer's emotions as thousands of people sing his/her song !!!
First of all, Grinus's link's dead, here's a good one :
https://www.youtube.com/watch?v=JoZ6P6ihzCU <- Lara Fabian - Je t'aime (Live in Paris, 2001, HQ) - Very touching, considering it was the first concert couple of weeks after her husband passed away
Now some other enjoyables:
https://www.youtube.com/watch?v=l9H3IgM-ViU <- Beyonce live at Glastonbury - Irreplaceable (BBC)
https://www.youtube.com/watch?v=tRnFHfI7WAQ <- Paul McCartney - Hey Jude Live at Hyde Park
Many others (there's a good reddit thread easily findable "Best videos/instances of crowd singing together at concerts")
My personal three favourites - The big guns:
https://www.dailymotion.com/video/x5ufor <- Patrick Bruel, J'te le dis quand même - Best female energy ever (young girls LOOOOVED Patrick Bruel)
https://www.youtube.com/watch?v=Zklqr1xj32Q <- Blind Guardian - The Bard Song (every bard's song live is epic ^^)
https://www.youtube.com/watch?v=cZnBNuqqz5g <- LONDON, ENGLAND Green Day Crowd Singing Bohemian Rhapsody - Hyde Park July 1st, 2017 (yes 2017, so no singer ^^ !!!)