Personally I haven't found any of the RE games I've played to be hard, but for some parts fairly annoying. The toughest part in the games has propably been the last bossfight in Gaiden: I didn't have enough healing items (but my team had the best armors) and I ran out of ammo on every weapon and the knife just won't work... I had to cheat to get infinite ammo on grenade launcher and he still wouldn't die until a few minutes of continuos shooting
The game itself wasn't that bad.
And I haven't played CV (yet) so I can't say anything about that one but my friends who have that game have said it's hard.