Okay, before you start typing "WHAT ARE YOU SAYING LOTUS? ARE YOU INSANE?", listen to me, to why I think that GW2 has the best progression system in any MMO so far. I played Ragnarök, Perfect World, World of Wacraft, Rift, Runescape, Lineage 2, Tree of Savior, Mu Online, and many others. Most of them offer good progression systems, Ragnarök being my one of my favourites as well.
But I think that Guild Wars 2's progression tops all of those MMO's - GW2's progression is great: You level up with everything, and most of the content is easily accessible, even at early levels. It may be more casual, yes, but it still fun as hell. Yet, people complain that GW2 has no end game. In the early days, I kinda agreed with that statement. Sometimes you feel lost, because technically you don't have anything to "look out for", to "achieve".