I've run every 5man at proper level. Would of voted classic WOW by design but its not on the list (unless i missed it). You could spend so much time in there and they actually felt like dungeons. Voted TBC heroics because they were the most challenging and required flawless cc/coordination; I just overall enjoyed them. I liked WOTLK but they were too easy. Cata's were boring and I utterly despised MOP's in every aspect imaginable.