Originally posted by Jetmech Jr.
We're not talking about there ships, we're talking about the Shivan THEMSELVES, so this point is moot 
The battleground is important.
taking all into consideration, I think I'll change my opinion to hesitant shivan win. More than one xeno, though, or if its the queen...
So you declared most of my points moot on the basis that they considered multiple combatants, then added a proviso to your own analysis based on....oh, look: Multiple combatants.
Against a Xeno, Warrior Bug or Predator, a Shivan would kick the living **** out of its opponent and rape their crushed remains.
The Xeno would be torn to pieces without a second thought. It wouldn't even be worth warming up the bio-cannon to vapourise.
The Warrior bug MIGHT tear the Shivan up some with its mini-spikes above its eyes, but the Shivan could just leap over its head and tear out its nerve stem from behind, or plasma it from afar.
A Predator might have a chance inside a complicated, factory-like environment where it could set traps and make hit-n-run attacks, but in a simple battle arena the Predator would be backed into a corner and torn to pieces before it could even think about attacking.
The Shivans as fast as and stronger than most non-humanoids (Bugs); and they're tough and strong enough to stay standing till they get a chance to make a single-hit kill on faster, humanoid targets.
The only thing that could threaten a Shivan is an Alien Queen, which could possibly spear the Shivan in the head before it had a chance to plasma the *****.