Agreed--if anyone else is struggling with this decision, play all five games (in order). Not only does playing all of the games provide necessary pieces of storyline to fully appreciate the last game, it allows you to see just how far Wadjeteye has come in its ability to put together a solid game. The improvements in graphics, game mechanics, and overall playability over the course of the series are astounding.
One caveat: Because the playability of the games increases so dramatically from the early games to the final games, some people may find that they don't want to keep playing through the entire series. No one should get discouraged, though. The early games are short enough to make some of the more frustrating mechanics tolerable. At any rate, please be assured that playing through the entire series is very, very worthwhile.
Post edited December 19, 2014 by infinityeight