As a Gran Turismo fanatic, I still prefer the Standard Edition. This is like asking this alternative question: buy tickets to one game, or buy season tickets? It would depend on how much of a fan you are to something. If you're willing to pay more than you have to in showing your love for something, you would get the best package to fulfill your fandom no matter how much it costs. Being the old-fashioned person I am, I'm intrigued by a Collector's Edition or the Ultimate Edition, but I'd rather get the Standard Version. All I care about is getting Gran Turismo 5. I do love the extra things you get with the other packages in addition to a copy of GT5, but I wouldn't want to waste more money than I'd like to just to get my hands on GT5.
Therefore, tab me for "Standard Edition."