I hated GW1... and I don't see why I'd like GW2. It takes all the aspects of RPGs and MMOs that I DON'T like and puts them together.
Excessive instancing with almost no chance of grouping - check! Henchmen, which may be useful in general, but often only make it harder to find a group - check! No actual open world PvP, or open world in general -check! Inability to jump, which I hear will not be there for GW2, check! Inability to go beyond a small area where you're "supposed to be" - check !
And by the last thing I mean that when I see a bridge over an endless hole I should be well DAMN able to jump down the hole. I HATE when games restrict you from jumping off something, climbing something, or force you to look for a new route if there is a fucking branch in your way.
And yes, I'm well aware that Guild Wars 2 will supposedly change some of these things... but urgh. I also hate the style of the game. I do like anime and things like that, but most of the armor, especially for female characters, really pisses me off. If they can't come up with something good, just give all the casters a damn robe instead of some fucked up half invisible dress. Caster = robe or tunic, no matter the gender.
And no matter how I may dislike WoW, I can guarantee there will be no wow killer, ever. It doesn't work like that. Look at freaking UO and DAOC. There are still people playing either. And chances are, some people will still be playing those games in 5 years. Or even in 10 years.
Same goes for WoW, but with higher population, you might expect a lot more people to keep hanging around.
Edit: I also hate most of the combat system in GW. Dodging projectiles is a nice touch, but the rest of it is just urgh. Most of the PvP I remember doing back on my warrior (Or whatever you called them in GW, I don't even remember, it was a while ago. Some time when Factions were just released) consisted of running up to a person thanks to the whole approach of the game doing EVERYTHING for you like running towards target, keeping it in front and everything, and hitting them repeatedly to hopefully build up adrenaline or whatever they had in place. Which was also a stupid system. At least, in WoW, you knew where you were going with each hit. Here...perhaps I didn't bother to look into it long enough, but how the hell does a costly adrenaline ability appear before the cheap one? When the cooldown wasn't triggered yet? And other roles were little better.
Also, just 6 spells ( or was it 8?) was a major annoyance.
And, just to complete this rant, I HATE GAMES THAT REALLY, REALLY FORCE YOU TO STAY ON A SMALL PLAIN/ZONE INSTEAD OF EXPLORING OR BEING ABLE TO CLIMB OR JUMP OVER THINGS!
I hated it in KOTOR, I hated it in KOTOR 2, I hated it in GW, and I hated it in every other implementation.
If I want to jump to the endless pit of doom, I should be damn able to.