Was it the Greek Hoplite,
The Phalangite was arguably better than the Hoplitai.
Pre or Post-Marian reforms? And then, are you including Limitanei, or is that only Comitatenses?
Surely you meant
Panzer Grenadier by that.
They weren't really the best soldiers in the world, they were simply some of the most famous. Still elite troops, though.
the American Marine, the list could go on forever which is exactly why i didn't do a poll and me and my history teacher never really got to a clear cut agreement so I'll ask you guys what was the best ever.
Well you have to remember that you cannot compare things like legionaries to United States Marines to Redcoats to Beoduin, each is in its own element. Perhaps you can measure how they fared against other soldiers of their day, and attempt to decide which was the most dominating relative to its timeframe, but to establish a "best soldier ever" would be completely subjective in the end.
Here are my nominees from various eras.
Ancient - Assyrian Charioteers
Archaic - Iron weapon-wielding Sea Peoples
Classical - The Sacred Band of Thebes, or Spartates Hoplitai
Hellenistic - Pezhetairoi
Roman Republic/Empire - the post-Marian Comitatenses
"Dark Ages" after 476AD - Mohammad's Ansar warriors
Middle Ages - Mongol Cavalryman
early Gunpowder Era - Janissary Corps
"Age of Imperialism" - Prussian Fusilier
WWI - I'm not qualified to make this call
WWII - certainly the
Leibstandarte Adolf Hitler and
Das Reich divisions of the
Waffen-SS
Postwar - United States Marine
These are of course my own suggestions, quite without elaboration; should it be requested, I would be happy to expatiate copiously.
EDIT: I'm also aware of my ignorance of Eastern and pre-Columbian American styles of warfare, and how Western-biased this list is.