It would make a lot more sense to have one standard video format, but it didn't happen like that. Here's a paragraph that stood out for me on one site:
There are three dominating standards in use around the world, NTSC, PAL, and SECAM. These three formats have developed in different parts of the world for historic reasons. Since so many televisions and VCRs are already installed everywhere, it is hard to convert everyone to one standard.
Unfortunately, it doesn't mention those 'historic reasons'. But seeing as video game companies divide their video games into regions (similar to DVD regions) even if there was only one video format, Europe, Australia and other countries would most likely still be getting games at varied times from the US. You also have to take into consideration local holidays - big releases generally come out sometime in November to get the Thanksgiving sales. I have no idea what Thanksgiving is, but I know it involves turkeys, guys in black hats and apparently presents. Whereas in Australia, the hot games are usually clumped together in mid-December for Christmas, making buying games a real headache at that time.
There's all sorts of factors that affect game release dates - holidays, conversions, language translations, trademark issues (for example, the whole "Starfox/Starwing" thing) and sometimes, games are only released in certain countries, causing problems if sequels eventuate.
One big example of this is the whole "Gameboy Gallery/Game & Watch Gallery" thing. In Australia and Europe, a really simple game called Gameboy Gallery was released, featuring a couple of Game & Watch games. Later on, Japan made a game called Gameboy Gallery, which came to the US and Europe as Game & Watch Gallery, but to Australia as Gameboy Gallery 2. Subsequent sequels followed this trend, with Australia reaching Gameboy Gallery 5. To further confuse things, Japan brought out Gameboy Gallery Advance. It was brought out in the US as Game & Watch Gallery 4, and to Europe and Australia as Game & Watch Gallery Advance. (Australia probably got tired of re-editing the manuals and Title Screens for such a trivial reason, and started afresh).
So there you go. Take away the PAL/NTSC problem and you'd still have a whole slew of other things to cause you to wait for your favourite games. Metroid Prime is quite good though, and I like it even though most 1st person games just make me feel sick. There's additional stuff added to the PAL version of Metroid Prime to compensate for the wait. I know there's more difficult gameplay (ex. lava eats away at your health much faster), voice narration, new movies and tougher enemies. Have fun.
And now I sleep.