I racked up 2.400 hours before the Steam release and let me tell you why I stayed faithful to this MMORPG:

It respects your time!

Took a break from the game and want to continue where you left off, without the need to grind to a new max level or gear-score? No problem, press play and have fun.

Some players prefer vertical progression while some favor horizontal progression.
Guild Wars 2 offers the later and I wouldn't want it any other way.