I always liked Transformers slightly more than G.I. Joe, but it was cool that they were both out at the same time. Hasbro fucking owned my ass from 1984-86. Fortunately "Star Trek: the Next Generation" debuted right after the 2 shows evaporated.
Funny how whenever one thing I liked as a kid went away, something new popped up at just the right time for me to enjoy.
Basically:
Star Wars -> GI Joe/Tranformers -> Star Trek: TNG/DS9 -> Buffy/Angel -> Wrestling -> Battlestar Galactica.
Voltron, Thundercats, Batman, X-Files, Highlander, and Farscape all fit in there somewhere, but the above 6 eras above were the biggest geek-fests for me.