Warcraft III was the bases of my reason for purchasing WoW back in 2004, I loved the story, characters and gameplay which passed on through vanilla, TBC and WotLK. For me, WoW was the continuation of where WCIII:TFT left off and after killing arthas in WotLK and it was the conclusion for the series for me.
Having played from the beginning, Cataclysm was a let down for me (stopped playing 6 months ago). Less creative and ingenious than the two previous expansions, and the time for new content takes even longer than before. Alas, maybe its just getting old...but I put my blame on Activision, much like EA, that doom good franchises whenever they get their grubby hands on them (Westwood C&C)