I say game piracy was the best and worst thing to happen to the Amiga. Don't forget at its height the Amiga was THE games platform, us serious users were a minority that only became a majority in the Amiga's twilight.
It shames me to admit it but i bought my first Amiga 500 to play games after i went to a user group of meeting of about 300(!) Amigans who were happily swapping pirated games. No-one thought twice about it. The choice for most of us was: buy a Nintendo or Sega with expensive cartridges that we couldn't afford nor copy or get an Amiga that we could have pretty much whatever we wanted, often before the local retailers. For a 14-17 year olds with no money it was a no-brainer really. But it drove hardware sales to amazing heights.
But eventually, software developers started to hate the Amiga for the same reason. I'd say only 10% of their software that was circulating was legitimate. Ofcourse hardware advancement on the PC was a factor but the ease with which the platform could be pirated was very very important. So the software developers went PC with CDROM which was expensive to copy: cd-burners were over $1000 Aus, but eventually the software houses ended up in the same hole when burners became cheap. And thus PC ruled the roost, later overthrown by the Playstation which now was just as easy to pirate games for as opposed to the N64 which had the better games but on cartridge.
The most popular hardware platform was always the easiest to pirate games for. At its height, this was the Amiga 500.
Sad but true: Piracy made the Amiga, Piracy killed the Amiga.