The original one was the best. It had a very distinct atmosphere that has not been able to be replicated by the sequels, which started to balloon more and more into the shooter action territory and big spectacle. Well, the second one was pretty on point still, before the downhill began.
The first one, man. It really felt like you were alone in a weird and mysterious mansion in the middle of nowhere, trying to survive whatever horrors was going to be thrown your way. Little by little, the plot and the lore started to unfold. Umbrella corporation? What's that?
The fourth one seems to be universally loved. I mean it was good, but it sometimes felt a little aloof, just running around in the countryside and shooting respawning monsters. Really started the trend of action and flashiness over mystery and suspense. And the weird merchant thing was so awkward, it destroyed any sense of groundedness going forward. Just felt so gamey.