First, when did I compare Robotech to either of those shows? And secondly, what fan projects?
I knew four kids in high school (I'm in my mid-30's) who knew what Robotech was, and not a single one in my adult life (outside of those I've met on this forum). Without a true, dedicated toy line, the show was never going to be truly that popular (it didn't help that it had a really shitty time slot in many markets).
Robotech was certainly never as popular as Thundercats, which itself was nowhere near the levels seen by GI Joe and the Transformers.