obviously, the comics are not canon, since Hicks and Newt are alive. i guess the only things that can be considered canon are the movies. afterall, if they took the comics into account, Hal Jordan, Kyle Raynor (both Green Lanterns), Superman and Batman, along with the Terminators would all have mixed it up with the Xenomorphs.
edit: oops, forgot the Wild C.A.T.S and Stormwatch.....other teams which have fought the Aliens....