Nyman/Greenaway and Goblin/Argento are quite popular among film buffs or above-average culture-aware people, in my experience. I’m not sure I would call them underrated.
To be honest, in my recent posts I wasn’t thinking about tht under/overrated aspect as it does not make much sense to me due to the reason Nick just mentioned.
I think, these pairs are either existing in public conciousness or not so much. If we map “not so much” to underrated and “well known” to highly rated, I still have no idea what is here the reference group and what do they know.