Lunar Templar said:
also, if you play Zero Mission, there's really no reason to play the NES Metriod cause ZM is just a retelling of that games events with more stuff added in.
I disagree: while Zero Mission is supposed to be a remake of the original Metroid, it feels like a completely different game that just happens to have a similar map layout.
Zero Mission plays a lot Super Metroid and Fushion. If you liked either of those, you're also definately going to like this. I'd also say it's a good introduction to the 2D Metroids: while I think Super Metroid is somewhat better, Zero Mission might just be a little more friendly to newcomers.
The original Metroid, on the other hand, is very different from the modern entries in the franchise: there are no maps, so you'll have to draw them yourselves; it also throws you into the deep immediately and never really gives you any direction of where to go, you'll have to figure that out for yourself. This can be seen as a good or a bad thing, but it's definately not for everyone.
Metroid is also pretty damn hard: I'm currently playing through it and not doing very well. For a large part this is because, when you continue after dying, you only get 30 life (regardless of how many energy tanks you have) and enemy drops barely do anything to replenish it. This is a very annoying form of fake difficulty and a major design flaw that ruins most of the game in my opinion.
Either way, you can unlock the original Metroid by beating Zero Mission, so just buy that one.