A low-risk, low-reward game from Nintendo. You're gauranteed to have fun, but you're also gauranteed not to be blown away.
Zero Mission is a remake of the original NES Metroid with Metroid: Fusion graphics and controls. Naturally, its good in the way all Metroid games are good. There are then two reasons to get Zero Mission: desire for more Metroid, and nostalgia.
My memory of the original Metroid is very hazy, so I couldn't really reminisce. Judged on its own, its a very good game, but (naturally) not much is new. Even if you've never played Metroid, if you've played Super Metroid and Metroid: Fusion, then, for all intents and purposes, you've already played most Metroid: Zero Mission. In fact, most of the villains are identical to villains in Super Metroid. The main downside to the game is that there isn't much there at all. The game is even shorter than Fusion (less than 4 hours at a leisurely pace), and there are very few bosses. Because its a remake, all the equipment and weaponry is old stuff.
On the plus side, there is a nice new area after the death of Mother Brain. SPOILER SPOILER SPOILER: There's even a stealth section of the game in which you play as Samus out of her suit. Very neat indeed.
Die hards will love it, and newcomers will enjoy themselves. Its not a great game, and its not a must play for every gamer. Still, Metroid can't possibly be anything but good.
GOOD: Metroid is always insanely fun; a great new area after mother brain.
BAD: Insanely short; 75% of it is stuff you've already done in Fusion and Super Metroid.