Probably Resident Evil 4 on PS2 or Shenmue 2 on the original Xbox.. the conspiracy theories and downplaying were nothing short of hilarious.
Edit: and the PS3 price announcement at E3 2006 - the most rabid and loyal PS/PS2 enthusiasts suddenly cared about Xbox Live and offset analog sticks after mocking the original Xbox for years.
Bet with Einsam_Delphin: http://gamrconnect.vgchartz.com/thread.php?id=172355&page=11