Lots of good releases in this time span, but these albums are at the top, in my opinion:
2009 - Voice of Steel (Nokturnal Mortum)
Runners up: Across the Dark Insomnium
2010 - TIE between: Marrow of the Spirit (Agalloch); On Divine Winds (Hail of Bullets)
2011 - TIE between: New World Shadows (Omnium Gatherum); Ghost (Devin Townsend)
2012 - TIE between: Epicloud (Devin Townsend); March of Progress (Threshold). I may give the prize to Threshold. This is one of my all time favorite records - every song is a standout with most approaching the level of excellence in craftsmanship that few bands can reach.
2013 - Surgical Steel (Carcass) Valkyrja; (Tyr)...bumped to number 2 spot, but a majestic record. For non metal, another top of the year record is Departure Songs (Hammock). An unbelievable achievement of post-rock glory. Maybe the best driving/chill out/beach music ever.
2014 - Promulgation of the Fall (Dead Congregation); for non metal and just a demonstration of pure song writing prowess, Casualties of Cool easily would be number one.
2015 - The Malkuth Grimoire (Alkaloid)...Yea the year isn't over yet but I don't see anything on the horizon even close to topping this.