To claim to have the Best Soldiers in history, a military force has to refer to all aspects, not only combat ability.
The Vikings were the most talented sailors of their times, and their knowledge of navigation did not become available for other people until the 15th century. They were also masterly skilled swordsmiths, and top level fencers. But they were disorganized, being more freelancers than regular military force.
The Mongols were the best organized and disciplined army of their time, advancing almost as fast as the 20th century mechanized armies, but their logistic system lacked almost totally, their economic basis being the pillaging. Not very smart. Almost the same for the Huns/primitive Magyars.
The Japanese Samurai were the best absolutely swordsmiths in history, and their fencing talent was legendary, but their rigid structure made them unable to evolve, to adapt themselves to modern weapons and tactics.
The Medieval Magyar cavalry archers, subject to the great admiration of Magyar members, disgraced themselves in their battles against the Turkish musket-infantry(Janissaries), showing the inability to adapt themselves to modern tactics, like the Samurai.
The Romans were the greatest military force of their time, both in warfare and peacetime, but they were too far back in time to be comparable to any modern military force.
The best ever soldiers of the pre-mechanized era must have been the Russian/Ukrainian Cossacks. Qvist's remark about them is as wicked as false. The "Comanches of the Steppes", as the Westerners had named them, were actually the best cavalrymen in history, learning to ride horses soon after they learnt walking, living in a structure united by kinship and military comradeship that accustomed them to military discipline since their birth, master horsemen and sword fighters, and also second only to the Samurai in swordmaking. They adapted themselves over the centuries to firearms(the death of European knighthood), becoming first-class marksmen. They lived through all kind of warfare, fought all kind of enemies, hold the flag high during the Russian military debacle of WWI, resisted to the entire Red Army during the 1919-1920 battles in the Don region. 8)
The best military force of the mechanized warfare must have been, on the other side, the Waffen SS. Equipped with second-rate weapons and equipment
(they should have thanked for this to Heer bureaucrats), they fought like hell for almost six years, from the mud of Poland to the frozen plains of Russia and the Ardenne valleys. Not all of them, of course, but 12 of the 38 Waffen SS Divisions(not all of them composed of Germans) might have been the toughest military force ever seen. 12 Divisions = 240,000 of the finest fighters of Europe. The multi-national army raised by Hitler to stop the Red tide had proved its value on the front. After Hitler's change of speech of 1942, when the quest for Lebensraum was replaced by the need to stop the "barbarians from the East", hundreds of thousands of young Europeans had joined the SS. The news journals of 1943 shown long queues of boys waiting to the SS drafting commision. From Norway to Spain and from France to Ukraine, they went to fight to save the Europe. Some of the most admired military commanders in Germany were not of German origin - Miguel Ezquerra and Leon Degrelle are the best examples.
As for their battleworthiness - just let's say that the worn out, poorly equipped and surprised Waffen SS men had wiped out the Allied paratroopers, while the 17-year old boys of the 12th SS Hitlerjugend had resisted the Allied tide under impossible conditions. And these were regular troops. I think the men of Otto Skorzeny could have made hamburgers out of any US Marine(and then cook the hamburgers with a Flammenwerfer 41).
8) The way Skorzeny was loathed by both the Westerners and Commies shows they feared him like hell.