Meb's winning time was better than every winning time since 2001 other than 2006, 2008, 2010 and 2011 (massive tailwind). Barring 2011, which I think you need to throw out as an anomaly, Meb's winning time was the 4th fastest out of the last 13 editions of the Boston Marathon.
In 2010, his time would have finished 3rd (note, he finished 5th in that race in 2:09:26), in 2008 it would have finished 2nd and in 2006 it would have finished 3rd (which, incidentally, was Meb's place that year in 2:09:56).
Meb: 2:08:37, winning by 11 seconds was a very very good performance, inline with past winning efforts., Also, 2nd and 3rd had phenomenal races as well. Look below to see which years since 2001 produced slower times then this yeqr with the differential to 2nd place. This year's race was actually significantly deeper than the large majority of Boston Marathons since 2001.
2013: 2:10:22 +5
2012: 2:12:40 (I think Korir was a bigger shock then Meb) +26
2009: 2:08:42 +70
2007: 2:14:13 +20
2005: 2:11:45 +36
2004: 2:10:37 +72
2003: 2:10:11 +23
2002: 2:09:02 +3
2001: 2:09:42 +24