I'm totally anal when it comes to that. I HAVE to play any game with sequels from the beginning. If nothing else, than for the fact that you can miss out on humor or helpful hints that would help you find something you'd never normally find.
But on top of that, it helps you have a point of reference. It prevents you from buying the sequel, going "OMFG THIS IS THE BEST ****ING GAME EVER", only to find out the game was a flop, and it's predecessor had done much better, with higher ratings overall.
