I think that some of the later more choral-dominated oratorios are deservedly famous, even when the overall dramaturgy might sag sometimes. E.g. "Solomon" does not really have much action to speak of (except the "harlot scene"), but the choruses are simply amazing and it is funny when Handel almost self-ironically lets Solomon give the Queen of Sheba an entertainment with 4? choral pieces each depicting a different affect/mood.
But the early italian pieces certainly deserve to be better known, although there are fortunately pretty good recordings around.
Maybe Handel basically copies the style of Alessandro Scarlatti and other older italian composers (whereas the specific stylistic fusion of the 1730-50s oratorios is his more individual "voice") but they are brilliantly done and lots of fun. And the same is true for the shorter Italian cantatas as well as the Dixit Dominus (and a few other motets/psalm settings from the Italian period).