Really, it's a bit ridiculous to compare the two, because the technology present in the Metroid series is on a whole different level than the comparatively primitive weaponry and equipment present in Halo. And that's before we take into consideration the Speed Boost, which also gives Samus access to the Shinespark (which I believe Dark Samus used for space travel, by the way), and the Screw Attack which grants Samus with near-invincibility and the ability to instantly vaporize most opponents.
And it's not just the tech; there's also the wildlife. Zebes as a planet was barely inhabitable by human life, but the indigenous life-forms of that planet evolved to survive in magma and extremely corrosive acid. On SR388 were the Metroids, who were capable of absorbing a variety of different energy types, including the so-called "life energy", whose only weakness was being frozen solid and shattered with multiple missiles. People suggest that Samus' Power Beam is weak, but the fact of the matter is that it's the wildlife that's immensely durable.
The way I see it, the standard Galactic Federation soldiers are probably a good bit weaker than the Spartans physically, but equipped with medium-range weapons that far surpass most of what was present in Halo. I truly doubt that the projectile weapons from Halo would have much of an effect on Samus' Power Armor... except for the rockets, which might just take out one of her 20-ish energy tanks.
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Also, at the age of 3 Samus was genetically altered by the ancient and almost mystical Chozo race, which without a doubt was the most technologically advanced civilization in the Metroid universe, in order to survive the harsh conditions of Zebes, giving her superhuman strength, reflexes and durability in addition to the Power Suit. She was trained as a warrior by the Chozo for 11 years, and then joined the Galactic Federation military, where she server for several years before becoming a bounty hunter. At the end of Metroid Fusion she was once again genetically altered, this time with a Metroid vaccine, and adopted limited Metroid-like absorption abilities. Until Nintendo decide to release an actual Metroid V, there's no telling what other abilities she may develop due to her recent mutation.