Roger Craig Smith was my favorite Chris, far better than anyone before or after him in the role. RE5 has the best Chris of the franchise.
Paul Mercier for Leon, I think he did a great job for him on RE4, however, he wasn't as good in Darkside Chronicles and Degeneration.
Patricia Ja Lee and Catherine Disher were both great Jills, and I would say they are pretty much tied.
To me Alysson Court will never be replaced as Claire., and for Wesker, all voice actors aside from the one in the original are good.