The biggest earthquake in our century is the Indian Ocean earthquake in December 2004 with a magnitude of 9.1. But that's not exactly in the last five years, so the Sendai earthquake in Japan today (March 11, 2011) is the biggest earthquake in the last 5 years, with a magnitude of 8.9.
The largest measured earthquake in last 5 years was the magnitude 9.0 earthquake in Japan on March 11, 2011. The Haiti earthquake in 2010 was the second biggest quake with magnitude 8.8. UPDATE: Official magnitude of the Japan 2011 earthquake was updated to 9.1 on Nov 7, 2016.