favourite boy would be translated literally with Lieblingsjunge. This sounds like something unsual to say, though, and depending on context the translation might be different.
Allemand (german boy) Allemande (german girl)
Junge.
English: "the boy" means in German: "der Junge" or "der Knabe".
German is my favorite lesson L'allemand est ma leçon préférée
"Junge" would be the correct way to say "boy" auf Deutsch.
starker Junge
Lieblingsspiel is the translation in German. It is translated from English to German. German is mostly spoken in the European countries.
favourite photo = Lieblingsfoto
"Sie hatte einen Jungen"
Er ist ein Junge.
Good boy translates as Guter Junge
Was gefällt dir am besten an mir