GW1 was some top tier shit. I can't think of another action / MMO / RPG game where the combat revolves around working your way through an enemy's defenses rather than being principally focused on just killing the enemy faster (it is present in some RTS games, though, in a different form, and in some tabletop games like MtG or various tile games). What I mean by this is that in a typical action / RPG game the combat is about killing the enemy faster than he kills you. Things like debilitating conditions or resource depletion are generally a waste because you're better off just killing the enemy faster. In Guild Wars, the defensive capabilities are so powerful that just going for straight up "kill faster" doesn't work (not to say there aren't pressure oriented team builds, or concepts like spiking, but these rely on more than just raw damage); if you just try to attack an enemy then their team's Monk is going to be able to counter your attacks without much issue; in a straight conflict of "how much damage can I deal nuking this guy" vs "how much damage can an average prot / hybrid monk counter" you'll never win.
Accordingly we have tools like interrupts, hexes that slow casting speed or disable specific skills, conditions that can be used to divert a Monk's attention or overwhelm their resources, energy loss (since energy is actually very powerful and losing it is a big deal, if an enemy stalls out on energy that's a huge advantage for you), enchantment removal, etc - and some of these are also defensive tools in turn, like inflicting Blindness to reduce an enemy Warrior's offensive capability, or using interrupts to shut down an enemy Elementalist's nukes. In turn there are some defensive measures that counter their own counters, like the concept of a cover enchantment to counteract removal, or Holy Veil to drop a hex that would otherwise have prohibitive consequences when trying to remove it (or to prevent a cover hex from working). There are offensive concepts like the spike (massive concentrated damage aimed at killing a target so quickly that the enemy can't get defenses or healing on him in time) and tools to counter that, like the Infuse skill or the human ability to notice that several enemy casters are facing one particular party member while doing a casting animation and drop Spirit Bond on him, expecting a large and abrupt amount of damage.
So in Guild Wars, at least for PvP, the game is more about outmaneuvering the enemy's defenses or forcing them into a condition of low resources (energy loss, too many skills recharging or players taken out of commission by amount of hexes, loss of health and energy to death penalty, used up their hard resses, etc) that gives you enough of an advantage that you can actually kill members of their party consistently, rather than just trying to deal more damage than the enemy.
This overall pattern of gameplay is, in my opinion, what made Guild Wars so great and involved, and I've never played another action or RPG type game that had this same kind of focus.