He was a great military strategist who fought numerous campaigns against the Empire, against Warlords and finally against what remained of the Empire. He then retired to his homeworld, Mon Calimari. Here he stayed out of trouble until a new menace arrived, the Yuuzhan Vong. He watched the conflict from afar and eventually suggested and directed a plan to trap a Yuuzhan Vong fleet and destroy it, along with the warmaster. He pulled this plan off with minor casualties.
For Fark users, Ackbar has risen to level of photoshop cliche, often used with the phrase "it's a trap!" or a variation thereof.