Based on how bmac_121 phrased his comment, I'd say Horford's contract is in the Top 5 among similar players on a second long term extension... and there is an argument for him being 1st depending on how much a person wants to consider age and potentially-career-threatening injuries (if we're talking long term deals).
This is the list of all the bigs and forwards who averaged a double-double last season while playing in 60+ games:
http://www.basketball-reference.com/...t=&order_by=ws
Tyson, Lee, Horford, ZBo, Howard, Noah, Hickson, Vucevic, and Asik.
Vucevic is still on his rookie contract, and Hickson only had a 1-year deal, so they are out. Z-Bo, Tyson, and Lee are on the wrong side of 30 years old, with declining skillsets, and each makes more than Al over the next few years (Z-Bo almost $18M next season).
That leaves Dwight Howard, Joakim Noah and Omer Asik.
Well first off: Horford is a better all around player than Asik, so Omer is out; we won't find one reputable NBA source or publication who would rank or take Asik over Horford, with contracts considered.
Howard is a superstar, but his previous max deal expires next Monday, so we can't use the term "team friendly" anymore... and he also carries serious injury risks right now (back injuries are nothing to mess around with), same goes for Noah (chronic foot problems) and Lee (hip).
So, like I said towards the beginning of this post, it comes down to how much each person cares about age and potentially-career-threatening injuries when making that comparison for frontcourt players on their second long term deal.