A lot of people like the longsword because it's such a practical well-rounded weapon. It has decent length, decent speed, and decent damage. None of its stats are really outstanding, but none of them are really bad either. It's short enough to fight with in groups and close quarters, and you can even use it with a shield if you want so that you don't have to worry as much when you're chasing down archers. I know that sometimes I like to bring a practice shield when there's a lot of ranged players on the server, and while it's not a huge help it's still nice to have. I see the longsword as kind of a plain standard-issue 2h sword. Nothing special, but it gets the job done.
With that said, I agree that it would be nice to see a little more variety. There are a lot of axes and blunt weapons that are actually really good but are underused. Maybe if the 'unbalanced' tags were removed from some of them people would use them more. The relative damage of some of the greatswords is also pretty low when you look at how much slower they are. Of course, if you buffed any of the underused 2h weapons it may upset the delicate cRPG ecosystem and cause a never-ending tide of '2h heroes' to sweep across the land, hiltslashing everything in their way.
