According to YouTube, these were:
1. the Susan Boyle’s appearance at the “Britain's Got Talent” show and her song, that made her debut album one of
the most popular music gifts this Xmas (120+ million views);
2.
David After Dentist (37+ million views);
3. JK Wedding Entrance Dance (33+ million views);
4. a trailer for “New Moon”, a movie which is represented in the
top Google searches for 2009 (31+ million views);
5. an ad spot
Evian Roller Babies ,which was recorded in the “Guinness World Records” book (27+ million views);
As for the music videos, globally YouTube users preferred:
“I Know You Want Me” by Pitbull (82+ million views), Miley Cyrus with her “The Climb” (64+ million views) and “Party in the U.S.A." (54+ million views); The Lonely Island “I'm On a Boat” (48+ million views) and some R&B from Keri Hilson – “Knock You Down” (35+ million views).
YouTube history