For me;
Marhawa desire > Heavenly island > Prelude to the fall
Marhawa is my favourite. I'm glad it's a re6 prequel and ı would say it overall has the best characters. I like how it ties into re6 well. Plus ı ship piers and merah. It also has better story than the other ones.
Heavenly island is also good but ı started to get more disappointed by it recently. It should had been a rerev games reunion. Really weird that parker appears but not jill. Plus raymond and jessica could have appeared too; rerev's cliffhanger.
Pttf is ok but too short. Wished it was longer.