Admiration for a worthy enemy is a basic value of chivalry. It can be found in Dante, referring to Saladin (he also admired Godfrey of Bouillon, of course); in Ariosto; and in Tasso, e.g. here. This attitude would last, more or last, until the beginning of the First World War included, ending with the installation of machine guns on planes. More about this. All in all, Ariosto had already foreseen that war technology would destroy chivalry.
Riccardo / Richard is an Italian warrior, a hero and an anti-hero at the same time. In Gerusalemme Liberata (1581) his name was Rinaldo, and his story was quite different. In the manuscript of Gerusalemme Conquistata, but not in the final printed version of the poem (1593), Riccardo was often called "Guiscardo," with an obvious reference to this famous Norman stock. Riccardo is in fact a Norman, whose ancestors came from Scandinavia; this allows Tasso to turn him into a Viking, a true berserkr, in line with the Old Norse mania of his late years, see his tragedy Il Re Torrismondo.
The statement, here made by Muslim observers, that "six" warriors like Richard would mean big troubles will prove all too optimistic: Richard will defeat a whole army by himself! -- though with the essential help of an IronMan-like super-powered armor.