I personally like Metroid Prime the best. It was the first Metroid game I played also. Metroid Prime didn't have a great story,but, it had nice graphics, great music, awesome boss fights, controls were great, immersive atmosphere and innovating gameplay centered on exploring. Other M is a close second.

What's yours and why?

The only Metroids that I've played were Corruption and Other M and I like Other M better.

Metriod Prime is a classic game. A story and cutscenes break and fragment the gameplay.  Cut-scenes should be to show a little bit of the level you are entering.  And briefly set up the game,IMHO

Well, it was this decade where I was introduced to the Metroid franchise, and it's grown close to my heart.

If I had to put them in order, it would be something like this...

1. Metroid Prime
2. Metroid Prime 3: Corruption
3. Metroid: Zero Mission
4. Metroid: Other M
5. Metroid Prime 2: Echoes
6. Metroid Prime Hunters

You can't see it, but there's a big giant gap between five and six. Not a big fan of Hunters... but the rest were pretty darn great.

1. Prime
2. Prime 2
3. Fusion
4. Zero Mission
5. Hunters
6. Prime 3

I haven't played Other M but from what I've seen and read it would be below Prime 3 there. The mistake of Prime 3, Fusion and Other M is to introduce a story line/voice acting; the mistake of Prime 3, Hunters and Other M is to make the game a linear FPS rather than the more open exploration of Prime and Metroid I.

Interestingly I'd rate the music composition in the same order. I believe there's significant correlation between game quality and music quality.

1. Prime
2. Prime 3
3. Fusion
4. Other M
5. Zero Mission
6. Prime 2
7. Pinball (yeah!)
8. Hunters

Hands-down, it's Metroid Prime.  Of the last decade, they go like this:

Metroid Prime
Metroid Prime 3
Metroid Zero Mission
Metroid Prime 2
Metroid Prime Pinball (yuk yuk)
Metroid Fusion
Metroid Other M

Hunters isn't included as it's the only one I don't own for some reason.

Let it sink in kiddies, after a while, you'll see why Other M is such a travesty.

1. Prime
2. Corruption
3. Other M
4. Prime 2
5. Fusion
6. Hunters

I found Prime 2 and Fusion to be rather dull for some reason, and that hasn't changed. Other M has been thrilling, but has too many flaws that hold it back from true greatness, though if i were to rate Corruption a solid 9, Other M would be just barely behind it, like an 8.8 or something.

Metroid Prime 2, it just improved on everything the first Prime did

1. Prime and Fusion
2. Prime 3
3. Other M
4. Prime 2
5. Super Metroid

I've never pkayed Hunters, Zero Mission, Metroid 2, or the original. Prime and Fusion are what introduced me to the entire idea of Metroid (though I had played Castlevania before either of them) and are still my favorites. Super Metroid hasn't aged well as Fusion was just BETTER from a mechanical standpoint. Other M is arguably the biggest risk taker of the series thus far and is still a great title.