This is for those who have played it. Which is probably everyone except me. I had the Collector's edition for GC back in the day but played OoT instead since it was more straightforward. Now I really want to play MM since I never got around to it. So is it worth it?

It is for me! Well I was gonna get a new one and leave the old 3DS XL to my daughter, so yeah.

Buying a 3DS just for MM? I`d say... probably not. But it would be a good game to have and play :^)

EDIT: Despite my comments, MM is actually my fav Zelda game. Don`t mean to bring it down....

Can you justify other game purchases? If so, yes. Otherwise get the VC version from Wii's virtual console (if you have a Wii/Wii U.) 

best zelda.
even without zelda, ganondorf, master sword, sages and all these zelda elements.
the game is unique.
totally worth, imo.

Yes, absolutely.

It's one of the top 3 Zelda games imho. But you'll have to pay more attention to the game and have more patience since the game is more complex than the usual 3D Zelda.

I see, i'm guessing each mask gives you a unique power.

I never buy a system for just one game so no imo. If you are interested in other games however, then yes!

You should probably know exactly what you're getting into first, and then make your mind up.

Majora's Mask is about side characters and sidequests above all else. There are dungeons and items and bosses like there always are for Zelda games, but the focus is on making everyone in Termina likable as people. If that means having aliens lobotomize a helpless girl...so be it. And yes, that really DOES happen if you don't do anything to stop it.

If that interests you, then Majora is totally worth getting a 3DS over. Majora's Mask has a special place in my heart because it's the E-rated game willing to go there. It's really quite unique, intense, and overwhelming, and not necessarily in the "great for everyone" way.

Not all of them. Most of them do very little other than change dialogue if I recall correctly. There are the three transformation masks, then some very useful ones like the Bunny Hood (makes you run much faster). Some somewhat useful masks like the Bomb Mask (your face explodes... can be used in place of a bomb but you take damage, but you can cheese it and not take damage if you use your shield right I think).

Then there are just weird masks, like this one that makes Link do a funky dance when wearing it, and that's it, or some masks that have very specific purposes for completing certain sidequests.

As for your question I'd say just play it on Virtual Console if you have a Wii or Wii U. There are many reasons to buy a 3DS but if none of those carry any weight for you then Majora's Mask is not a substitute for them.