PvP. Given that was a very large focus in the original, and will continue to be so in this, that's where a large part of the continued play value will come from. Yeah, I'd agree it's not the same feel as GW1, but that's not necessarily a bad thing.
And while the classes may see similar, I do still see a lot of uniqueness in each, mostly in how they handle the use of their skills. I noticed that each class has one or two core mechanic that's shared with only a couple other classes, if any. The Mantras used by the Mesmer, the Marks of Necromancers, the Conjures of Elementalists, etc. If anything, they seem to rely on different mechanics for each class, instead of vastly different effects. A lot of this is likely for simplicity's sake, since it's easier to define and learn a standard set of conditions than to need to explain how each individual skill works. It does mean that, indeed, each class is going to be applying similar effects. However, I think that's also something they're trying to mitigate somewhat through the combo system, where it pays to each be filling a different role. Just because the roles aren't set doesn't mean each player won't adapt their role to fit their style of play.
That's my take on it, anyway. No, it's not the savior of MMOs, but it is leaps and bounds forward in many areas that, until now, have been simply considered the norm by hundreds of MMOs, both Korean and American. Whether it fills its role as a proper successor to GW1 is yet to be seen, but I'm certainly seeing a lot of the foundation shining through.