We'll start with one of the biggest: Samus Aran, famous bounty hunter, saviour of the galaxy and all round kick ass hottie, vs. Master Chief, who is some guy in a suit of armour he never takes off that hides when he takes a hit and uses this thing called 'bullets' (whatever that is) for his gun. Oh, and he thwarted the plans of the Covenant, while Samus merely blew up something like 5 secret bases, several space stations, umpteen giant monsters, Ridley (at least 4 times), a planet and an entire dimension, as well as saving countless millions from a terrible and slow death by Phazon poisoning. But hey, let's make some comparisons.
Samus Aran (Tallon IV variant):
Armour: Power, Varia, Gravity and Phazon Suits. Vastly reduce damage taken, shields have a very long life.
Weapons: Power Beam, Wave Beam, Ice Beam, Plasma Beam, Phazon Beam, Charge Beam, Missiles, Super Missiles, Wavebuster, Ice Spreader, Flamethrower, Bombs, Power Bombs. Beams and Bombs have unlimited ammunition, carries up to 250 Missiles and 7 Power Bombs.
Equipment: Space Jump Boots, Morph Ball, Boost Ball, Spider Ball, Grapple Beam, Scan Visor, Thermal Visor, X-Ray Visor, 15 energy tanks.
Armour: Mjolnir Powered Assault Armour. Resistant to some damage, low shield life, shield recharges if out of combat for a while.
Weapons: Machine guns, rocket launchers, sniper rifles, energy weapons. All have limited ammunition or charge.
Equipment: Torch. Oh, and that useless AI, Cortana.
Samus finds Master Chief, scans him, then does one of the following:
1) Melts his face off with the Plasma Beam.
2) Wavebusters him into a spasming mess, also shorting out Cortana.
3) Freezes him then shatters him with a missile.
4) Annihilates him with a dose of Phazon or a Power Bomb.
5) Blows him up with a Super Missile.
Master Chief tries to take on Samus. His weapon does a puny amount of damage (even rockets only take off about 1/4 of an energy tank, and Samus is carrying 15) and one of the above occurs.
Master Chief runs and hides. Samus finds him with the Thermal or X-Ray Visor and melts his legs and arms off as punishment for being such a coward.
Master Chief tries to snipe Samus, but runs out of ammo before he's taken her energy down by a quarter. Samus hunts the idiot down and repurposes his body as a Phazon repository.
Metroids appear from nowhere and drain all of Master Chief's energy. Fail.
As we can see, Spartan 117 is dead no matter what happens. Admit it Halo fans, Samus Aran is a much better hero.