Gotta go with the late 80s early 90s too, i still remember seeing the ghost minfig, rodin hood, large castles etc for the first time. Up until then all i ever had was city sets and seeing all these new products really boosted my love for lego.
2005 is shaping up to being a great year for lego and it already looks better than the few years sets, but im not sure that we will ever see another age as good as then, but i sure hope so ;)