I wrote this post as there are many people that claim that dynamic events are basically the same having the traditional ! and ? questing that we see in pretty much every other MMO out there. I guess this is by large part due earlier zones having less and much simpler DE's than what ArenaNet has actually done with them later on in the game. From certain angles that might be somewhat correct, as in they are a form of questing. But there are couple of key differences that give them a whole unique FEEL which also defines Guild Wars 2 throughout the game.
Here is an example of short DE I went through last night. My 20'ish charr ranger approaches a village next to a lake and as I get close enough, I see that there is an event going on. Seems like these merfolks are capturing village people and they need to be defended. There are already few players fighting them back and protecting villagers, I arrive about halfway through the event. The UI gives me 2 pieces of info: The amount of attacking merfolk and amount of not captured / total villagers. There are 5/8 villagers remaining and about half of the merfolk. So I join the fight and start smacking things around, trying to protect the villagers whenever possible. The fight was pretty tough, but we end up 'winning' with 3/8 villagers remaining. Notice the ' - marks around winning, as this is where dynamic events get interesting.
While we did complete the event and win it, there is a new event that pops up right away: rescue 5 villagers from merfolk lair. So bunch of us defenders jump into the lake and start swimming towards their base. While approaching we see few of the 5 villagers imprisoned in the merfolk lair which is ofcourse this awesome underwater construction of wood and mud. One awesome underwater fight later we save those villagers and they return to the village, proceeding to do whatever they were doing.
That whole thing was awesome, fun, challenging and interesting event with clear story and purpose behind it (merfolk are evil and they eat villagers.. or perhaps some player dived in their base and killed a bunch, angering them. Who knows. DE's have various ways to trigger them). No walls of quest text or anything, just pure action, reaction and story that forms around it.
Now lets visualize this same thing in ! and ? questing.
My troll hunter arrives to a village next to a lake. There is a guy with yellow ! above his head. I click him and skip the wall of text. There is new quest indicator in my map and I head to the beach where bunch of merfolk are staticly sitting around. I kill them untill my counter hits 10/10, I return and click a guy with ? who gives me another quest. I go to the underwater area that quest indicates, kill few merfolk and click on these villagers to free them. 5/5, so I return to quest giver to get my reward, while I can already see the villagers I just 'rescued' respawning behind me.
It's a nobrainer to me which system is more interesting and offers far more possibilities. The DE I described was quite a simple one with only 2 phases as far as I know. There of course might be more as I had to logoff right after the event and there could have been phases that led to that conclusion. The kicker is: IF we had managed to protect the villagers so that none would have been captured, the next phase would not have happened! There might have been different phase or the whole event might have ended there but outcome would be different.
The basic mechanics are the same in both styles, of course they are. You kill, you protect, you interact, you follow. The basic MMO stuff. But DE's give all this a purpose and meaning. Two guys on same area few hours apart could have radically different questing experiences depending on what is happening and how events are progressing. Instead of reading about the story you actually get to experience it happening and have a chance to change it!
This is why DE's are great and I cannot understand why anyone would argue they are not any different from your run-of-the-mill questing. Like many things in Guild Wars 2, on mechanical level they are fairly basic. But things tend to go far deeper than that, this is where Guild Wars 2's reinvention of the genre lays.
EDIT: Why this blog doesn't really touch WAR's public events or RIFT's invasions is because neither of those is really your main way of progressing through the game or telling stories. Both also have mechanical problems that cause them to be less glorious than they could be, they are not as dynamic or persistant as Guild Wars 2's vision of events. DE's are evolution of these, you could say they are PQ's done right.
Both RIFT and WAR still have the standard questing described in the main article as their mainstay.