In reality, Gunbuster came (a long time) first. But both have that 'best-of-the-best-athletes-going-against-each-other-for-the-Prize' thing going on. Both have some fanserivce. Both have comedy. It's when the real-deal dramatics start kicking in (the war, the Gunbuster proper, the relativistic speeds and whatnot, in Gunbuster's case) that things take a split.