The hardest I've beaten is Metroid Prime.
Of course, I've only beaten MZM and Prime! :P

the hardest for me (and probably everyone else) was the original metroid... wait, If you have beaten metroid zero mission then that means you have access to the original metroid in the options.

Normally, yes. But my ZM cartridge is beat up, and my memory is as good as dead... I'm hoping to play it on Prime, though.

I have played (not beat) the original though, and boy, was it hard! (until I used Lapras Sword cheat! :P )

then you would need fusion. I have passed the original without any cheating passwords. fusion is my favorite game in the series, it's the easiest too! (at least for me) though, first time is harder.

I'll rank them, easiest to hardest (On easy/nomal mode).

Metroid Prime 3
Metroid Zero Mission
Metroid Prime Hunters
Metroid Prime 2
Metroid Fusion
Metroid Prime
Super Metroid
Original Metroid

I have never played Metroid 2 or pinball.

I used NARPAS SWORD too :D

The original is only hard if you don't use cheap strategies. Even when you don't, it's not really that challenging. I'd say it's pretty hard.
I use one of two methods to defeat Ridley. The first one is very cheap.
Get the Wave Beam and stand beneath him throughout the fight, blasting laser up his butt..Or you can simply freeze his hot balls with the Ice Beam and pound his face with missiles.

Kraid is the harder of the three bosses because he can move back and forth(!). You can use a similar strategy against him. Freeze his...Flying nipples...and blast his face with missiles.
If you have a high amount of energy, you can go into Morph form and bomb him to death.

Metroid 2 is a bit different. At the end of the game you'll have to face off against Omega Metroid. The Omega Metroids actually fly around, instead of standing in one place, and you can only damage them by hitting them in their backs. You can not freeze any projectiles and they can, and will, push you into a corner if you're not careful.

I think Metroid 2 is the hardest game in the series.
Someday I will replay it to see if my skills have improved. Maybe I will use Kuro's freaking awesome map to help me hunt down more items.

I really need to play Metroid 2...

Yeah, who wants to play metroid pinball anyway? I used to be a pokemon fan, so I guess I said LAPRAS instead of NAPRAS! :P yeah, the only reason original is harder than ZM is the controlls.
I also used JUSTIN BAILEY but I liked NAPRAS better...
LOL it makes me wonder if they put it on there on porpose! :P

Yeah...It's still called NARPAS...

The only time I used cheat codes was for original. The only time I used a 100% walkthrough (not all the way through though) was for metroid prime 1.
Yaaay!!!11!!!! Phazon Metroid!!!!!111!!!!!!

Blurghhhh original uuurgh

When you get to the stage where it is 1000 posts between ranks then you can celebrate.

yeah, youre right..... 75 aint that much...

Context?

What about it?

unfortunately, pb can't ever be bothered to read the posts directly above the new ones, so he is forced to ask strange, already answered questions. Don't worry, you get used to it

ok. back on subject........