Hmm, tough question! I suck at picking a favourite RE. They're all so good :/ Ok, I'll use the elimination method.
Not 0, because Rebecca is icky and I didn't like the story, and not the dropping items anywhere thing. Playing as two people was good though, but not good enough to help this game.
Not Code Veronica X. Even though this was an entertaining and freaky game (Alexia and Alfed), it's just not my fauvorite. I didn't quite capture what had happened between RE 2 and this one. The weapons was pretty neat though, but the bowgun sucked.
NGH, these last three is hard to judge. However, I'm going to pick Resident Evil 1, mainly because I think resident evil should include an evil resident. And Resident Evil 1 had the most evil resident I've ever seen. This game horrified me through my childhood. Good job.