Macross was the secinf most popular show at one time after Gundam, but all the new shows that are coming out have already overshadowed it. In the US, Cartoon Network and Tech TVs have pushed Evangelion, Inuyasha into the forefront of anime. Not to mention Disney's support of the Studio Ghibli films.
Another thing that weakens Macross's popularity is that it's split by the Robotech factor. A lot of people that watched robotech still don't know what Macross truly is. I have a friend visit me last week that noticed my art books and even though the books don't have the name Robotech on it, he still called it by that name. I was shocked because here's a guy that works with web sites and the internet, yet he hasn't touched upon the subject of Macross vs RT. I'm not starting an age old argument. I'm just trying to explain a huge deterrence to Macross's true potential.
This and Skull Leader's explanation are 2 big factors to Macross's lack of popularity. I'm sure if the majority of the fans were given what they want, which is a follow up to the original love triangle, the fandom would pick up a bit more. But I got a feeling that's just too cliche for the Hory froating head. In any case I'm up for anything that comes next after Zero...