C47 is not only one of my favourite Hitman games, but one of my favourite games in general. Of course, part of that is nostalgia, since the first time I played it was when it came out, but, man, did it change gaming for me. It's got an atmosphere to it that can't be beaten. Such an innovative, original game.
Absolution on the other hand... Eh. Good stealth game and some cool hits when they actually appear, but when I want Hitman that isn't the game I reach for.