I really liked that King of the Mountain with the X guys and Ultimate X from Bound For Glory 2009. Apart from multiman matches and Sabin/Shelley, like somebody said above, everything was average. Joe/Homicide and Joe/Daniels for the X Title should have been tremendous, but it sucked.
But I think the hottest year for the x division was right around 2006
NOTHING can top TNA 2005, even the WCW or NJPW Jr. Heavyweights at their prime. 2005 was full of phenomenal single matches (like Joe/Styles from Sacrifice and Turning Point or Styles/Daniels 30 minute iron man matches) and multiman matches (best Ultimate X ever from Final Resolution, legendary Unbreakable 3 way, amazing 4 way match from BFG preshow, etc).
I'm not a fan of X-Division in 2006. The first three months were good (continuation of AJ/Daniels/Joe angle), but the rest was meh. Low Ki is great, but in my opinion his title reign sucked and the rest of 2006 with the belt changing hands few times around AJ, Daniels and Sabin wasn't that good either.