I hate to be cynical, but a few holes in the fighter repertoire is going to help sell copies of Martial Power, PHB2, etc. It's collectability.
Historically, greatsword could mean a lot of things, but in terms of a battlefield weapon, it generally meant a lot of control and the ability to attack armor at the joints. Hence, + hit. Because of the D&D abstract system, it should do plenty of damage, too; I do not agree at all that a greataxe would do tons more damage. The greatsword is faster and can be used more precisely, so they should be similar.
Worrying about 0.5 damage for a basic strike is truly trivial. How could you even bring yourself to care? The things to wonder about are, how does a greatsword do with various powers and feats? That's it's real output. As pointed out above, hitting with your encounter powers is nice.