"BLah BLah isn't fair because the [aliens/marines] don't have a counterpart."
It is the differences in the 2 teams that makes this game so awesome. If you want everyting the same go play some Vannilla CTF. There you can have all the excitement of 2 teams differing only in Model Color, playing on a flipped map, chasing a silly little flag. Everything will be exactly the same and you can all spam rockets at eachother until your faces clear up!