This kind of topic is prime bait for subjective responses. I hope you knew when you started the discussion that you aren't going to get a "right" answer out of this. But I will add in my two septims too; hopefully it's more constructive than anything.

If I can define a good pvper in a single sentence, wrapping all the fundamentals into one nice, pretty package, it is:
"a player who knows their own build and character so well that, in the midst of combat, they are focusing exclusively on what their opponent(s) is (are) doing, and reacting instinctively, rather than thinking about what they should do next."

In every duel, skirmish, large battle, zerg (you name it) that I've ever been a part of, this has been the "blanket" explanation for whoever won. Think about large scale AvA - two large, coordinated, experienced groups go up against each other (yes, we are assuming an ideal scenario) - which one wins? I know of one guild in particular (call them Group A) who is very coordinated and cohesive. I've seen them stampede and completely flatten groups. I've also seen the exact same group, on the exact same night get completely floored by the same group they had previously stampeded (call them Group B ).

Is it the strategy that's to blame? Not really. The reason that Group A failed their attempts later in the night is because Group B started acting in a coordinated manner. They previously weren't paying attention to their enemy; the enemy buffed up and prepared their assault, while the tank began baiting people in, and a moment later, Group A had both created and exploited a weakness in Group B's ranks. But later that night, Group B started listening to the raid leader, who was saying exactly what Group A was doing. He called out their actions, he called out what they were going to do next, and he called out exactly what should be done to counter it.

The same applies to a 1v1 or a small-group skirmish. Being focused on your own character, be it resources or buffs, means being at a disadvantage. Always assume the enemy knows their character better. Watch what they are doing. Anticipate what they will do next, and when it happens, react to it instinctively. Being able to react instinctively is the difference, at least in my opinion, between an average pvper and a good one. That split second we spend to think about what to do next, rather than just doing it naturally, is often the difference between victory and defeat.

The one who uses pots and poisons.

One willing to learn and have fun. So many times I hear the "exploiter/cheat" cry instead of figuring out what's actually happening. I've been indirectly accused of it, by a certain...vocal.. DC streamer. Nope, just leading a small, mostly inexperienced pvp group and doing something he didn't understand. If you lose the will to learn, it's easy to default to an exploit/cheat excuse, no matter how experienced you are. It's so easy to become jaded by pvp when you assume that you didn't win because everyone else is a cheater.

So having fun and keeping that interest in learning something new is what makes a good pvper imho. Giving a "good fight" whisper to someone who beat you in a memorable fight, having a sense of optimism and respect, working together with your buddies, these are things that make a good player great.