first of all: The Talent...
WWF just had the right people at the right time, starting for the top guys like Austin, rock and Angle, through midcards like D Lo Brown, Val Venis and The Hardys to the cruiserweights (Taka, Brian Christopher, Essa Rios), everyone had personality, everyone had a story and almost everyone was great in the ring. also it was the first time the WWF had a cruiserweight division, that, when it's made up of talented guys and not with indie flippy trampoline monkeys, it's allways entertaining.
The Storylines:
everyone in the roster has a story to tell, and Russo showed what he was able to do (unlike other times), there was comedy when necesary there was drama, emotional tension and it was epic over all... altough there were some flops like Mae Young giving birth to a hand, Mark Henry doing a tranny or a crossdressed Harvey Wippleman
The Overall Product:
with the rise of ECW, WCW becoming more edgy and MMA gaining notoriety, WWF had to adapt to the grain at the time if they wanted to survive, and they did it by embracing the 90s culture of toilet humor, hardcore matches and alternative rock/metal, making a fresh product, then the swearing and naked women (who were previously featured on both WCW and ECW) were a plus, so the Atitude era offered a well rounded, solid, entertaining and edgy product with good Wrestling (and "good wrestling" doesnt mean midgets flipping around the ropes or exchanging restholds for 2 hours, but having solid, physical matches with a story)
Young Guns:
and as much as i'm more of a WCW fan, i know WWF made the change every company needed that WCW didnt completely do until it was too late: pushing their young guns. i've allways been ad i'll allways be a huge nWo mark, but those guys were past their primes and young talent has to rise in order to keep your company alive, because nobody can Wrestle forever.
so the point is Attitude era had something for everyone