Haha believe me I've felt it... but you get what I mean. Guardians are superhuman, literally. Like almost celestial beings. With alien powers. They can cloak, teleport, and can even bring themselves back to life. I can't see how a spartan can handle a guardian. I don't mean like in gameplay but in lore. A real fight. To me a spartan seems like a highly skilled and shielded titan without any powers.