[Megalomaniac]

An Amiga was still better than any PC for flight sims and strategy games (even if money was no object) until every game was in VGA and hard drives became standard (and until the 640k limit had been properly overcome - says it all about how complex PCs were that 'expanded memory' (EMS) and 'extended memory' (XMS) had to be configurated separately)). After that, assuming money was no object, and you were patient with the technical side of PCs, it was starting to gradually change by 1991 (the end of the OP's question)

It's true that the PC got most great flight sims first, and better, after Interceptor or F16 Combat Pilot at the end of the 80s.

For adventures, losing LucasArts was a big loss (Day of the Tentacle and Sam & Max were as good as their Amiga classics, though their later ones weren't) but we still got Steel Sky, Bloodnet, Amazon Queen, Nippon Safes and a few others after late 1992 - though mostly after the PC versions and usually without AGA graphics. For RPGs we didn't get much after Eye of the Beholder II, apart from the Ishar series and the overrated (at the time) Legends of Valour, probably as much because they were more popular in the US than in Europe

It was later for strategy games though. Populous, Megalomania, The Settlers and Ports of Call (to name but a few) were all Amiga (or Amiga and ST) originals, and most great PC strategy games until about 1994 did get Amiga versions, usually available in AGA, although you needed a hard drive and at least an 020 to get the most out of them. The Settlers showed what could be done by an Amiga-designed game within a 1Mb A500 without lacking extras for bigger machines though.