It's a whole new game
Lately I borrowed a CD with old DOS games from a friend of mine. It featured also two PC conversions of Amiga games: Doofus and Jim Power.
The only game I could get to run was Doofus. To my surprise the game turned out to be very different from the Amiga original. Although it featured the same characters (a little boy and his dog), the level layout was completely different, it had different tunes and dissimilar graphics with lots of dark blue colours used. It was a completely different game with only the game's title and the characters sharing some similarities with the Amiga original.
Although I could not get Jim Power to run (due to the typical problem of not being able to free enough extended memory in DOS), I saw some fuzzy screenshots of this game on CD. The sprites looked much smaller and different graphics were used. It looks like this game too is very different of the Amiga original.
Does anyone know other Amigagames which have transformed in a whole new game during the conversion process to another system?