I think that a reboot was necessary for the series to continue on. I appreciate whatever contributions he had to RE4. I felt that in 2005 it was time to really move beyond the pre-rendered background in survival horror. I also think that the cult-imagery and the intenseness of dealing with a smarter enemy that was just as murderous as the T-zombies that used team logic to battle the player really helped to create a consistent thrill as the player was on the movie.
However, I feel that RE5 took it way too far. Instead of being scary, RE5 more or less felt to me like a mix of 28 days later and Metal Gear Solid 4. The scare wasn't there and the enemies were pushovers to the bigger and badder weapons. In the words of Darth Vader the game felt, "All too easy."