I think we already have one or several threads on this but since this forum is largely inactive I guess another refresh can't hurt
Both RE1 and REmake (HD Remaster).
The former largely for nostalgia, the latter for pristine survival horror gameplay that holds up today and nobody seems to be able to match in their attempts to emulate. Even Indie developers can't seem to get survival horror right because every new game I play that wants to do survival horror in spirit of classic RE really seems to fall short (with the exception of perhaps 'Ebola 3'). It's strange because it doesn't seem like it
should be difficult to make a great survival game with a small team of dedicated developers, but people seem to be struggling getting it right for some reason.
Anyway, since it's kinda scientific to determine your favorite based off numbers of hours played AND how well your opinion of the game holds up over time (favorability multiplied by consistency), both versions of RE1 and Rev 2 Raid Mode would probably be at the top. If my opinion of a game was determined PURELY based off of number of hours played, RE4 would also be up there as well, but since my opinion on that game has soured like milk In recent times, it simply cannot rank it as one of my favorites.
So yeah, RE1 it is