The Space Wolves or any Astartes chapter would win hands down.  Xenomorph to them are Tyranids on a much smaller scale.  Space Wolves can and will do the job, but Ultramarines (Tyrannic War with all it's veterans in the First Company or leading individual squads in other companies, Tarsis Ultra, etc.) or the Blood Angels (Space Hulk) would totally obliterate them.<br/><br/>And yes that's Boba Fett.  The helmet is green.