I'm quite fond of both games, but it's dangerous to directly compare them. GW1 is a Diablo style game that flirts with massive elements, whereas GW2 is much more of a traditional MMO. They certainly have plenty of things in common - a similar approach to/focus on PvP, similar action bar combat with a lot of attention paid to status effects - but they're not even really in the same genre, and GW2's focus on ad-hoc collaboration means that GW2 plays much differently moment-to-moment.

GW2 does some great things with quests, their PQ-ish Dynamic Events work well, and their huge raid-boss-y world dudes are a ton of fun. The way you can join multiple guilds and the way you are scaled down in level based on where you are makes it really easy to play with friends regardless of your individual progression. It's definitely worth a look.