Well that's what I get for talking in absolutes.. then again this is a lego forum..
Many of the other large ships (Galactic Enforcer included) tend to follow the same general shape, size, and design. The MX-81 was a departure from that, which I personally like. Now calling one of the top selling lego spaceships a "thing"... that's an unusual opinion.. :p
I say Alien Conquest was a decent effort, but I think they could have made it better. I like the lighthearted nature personally, but I don't think it drives a good set. Kids don't want Jack and Jane to happily explore remote corners of the universe. (well maybe my sister would) They want an Epic clash of multiple Alien species with large, highly armed fleets of spacecraft, robots, and tanks. Every popular space story out there involves significant conflict (Star Wars anybody?). Why shouldn't lego space?