The thing is the best Avengers stories (the original Ultron 2-Parter, finding Cap in Ice, Wonder Man's betrayal/redemption, Under Siege, the Hank-Slaps-Janet Saga among others) don't actually feature the Avengers doing the big things. In terms of the epic saving the world/universe stuff, there isn't a single Avengers story as good as The Coming of Galactus or the Infinity Gauntlet.
Hank Pym's biggest failure is Ultron, his biggest success is defeating a B-Team of the Masters of Evil himself. That's kind of symbolic of the Avengers as a whole. The Avengers are at their best when everything focuses on the interpersonal stuff and less so when they are super-police.