Pokémon Stadium (Melee) isn't all that bad. It's somewhat like Final Destination with the edges that gimp on its own. I'd say that stage is good for Ness, but that stage is pretty good for just about any character if they know what they're doing. If you want my opinion on all stages, I'll go ahead and just write some flaws out.
Battlefield
Basically this stage isn't bad for Ness, but it's not his best stage, either. You can still get around with aerial attacks, PK Thunder and a few other stuff, so it's not really holding him back.
Delfino Plaza
One of Ness' best stages. It's the best mainly because of the water which he really doesn't have to worry about recovering and the water spikes he can perform killing opponents at such low percent.
Yoshi's Island
Hell on Earth. That is all.
Lylat Cruise
Hell in space. Seriously, just look at the posts of these stages I've already written about.
Bridge of Elden
There isn't anything particularly wrong with this stage other than the fact that a Moblin leaves a gaping hole in the middle of the bridge. This stage is just wide that it reduces Ness' PK Jibaku and b-throw KO's. Of course if you're near the blast zone, you can just grab your opponent and 0% death them. Of course they can do the same to you.
Smashville
One of Ness' good stages. Despite the balloon that floats on by and the moving platform, Ness can safely retreat on the moving platform and use PK Thunder without him having to worry so much about getting hit. This is also good for when Ness recovers if you're to fly vertically instead of horizontally or diagonally. That balloon almost cost me a match, though! ]:<
Rumble Falls
I have no comment on this race track. I'll let you find what's good and bad about this stage for Ness.
Skyworld
This stage is only good for little boys and girls who do good deeds. Every character didn't pass this goal before passing on. Only Pit, Kirby and Meta Knight did, which is why this stage is pretty much good for them. Ness can uair through the platforms. I think. But this stage does no justice for his PK Thunder.
Castle Siege
The stage is okay for Ness. The beginning doesn't do good for his PK Fire since there is a slant. Of course standing on the other side of the stage in its first phase is good for using PK Fire. Just be sure not to get stuck under the edge of the castle. It's nobodies friend. The second phase is great for Ness. You've got two statues which you can build a fire pillar and when these are broken, you can go all out with your aerial attacks. The last phase of this stage is okay. It's like Lylat Cruise but more bearable for Ness. Still, when it teeters back and fourth, that could be bad for your recovery if you aim wrong.
WarioWare Inc.
I'm not sure what to make of this stage. Like Castle Siege, it has some phases of its own. There really isn't anything stopping Ness from being playable on this stage. Again, I don't know what to say about this stage.
Pokémon Stadium 2
Maybe I'm just weird, but I don't like going to stages that people say are good for Ness. I've read that this stage is good for Ness. I have no idea why. I prefer the Melee counterpart over this one any day. As I wrote about the Melee version, you have to know what you can do on this stage in order for it to be good for your character. I'd assume this stage is good for all characters.
Halberd
This stage is good and bad for Ness. Look at it like Battlefield but with one big platform in the middle. There really is nothing bad about this stage for Ness other than the landing on the ship and the slants that can stop Ness' PK Fire. Overall you've got your platform that you can use PK Thunder with and throw in some aerial attacks from under the moving platform.
Shadow Moses Island
Bad for Ness' b-throw if you love using it because the walls are in the way. However, breaking those down will help in the long run. Like the Halberd, you can just attack from under the platforms, pull some PK Thunder mind games and other odd crap you probably never thought you could do on such an enclosed stage. I'm positive you can start your own camp fire on the second row of the pillars when you're on the very top of the stage.
New Pork City
Nothing good comes from this stage. Seriously, this stage sucks for every character.
PictoChat
There are some stuff that will appear that might help you in a match. You got the two fireballs that float on the sides which you can throw your opponents into. Same goes with the spikes that appear on the far left and right of the stage. The face is annoying as he'll try to blow you off the stage. Of course you can go on his nose or forehead. But what's the point? The spikes that appear in a row of four, you can hide behind those and use PK Flash to annoy your opponent. You can also use your PK Thunder to bother them. If they're really close, swing your Bat.
Then there are those things that appear and look like a house. If you get caught in the box, simply try to use PK Thunder or something that goes through those solid platforms. The whale is just annoying. I'm not going to go through all the phases this stage has. I'll let you find out what's good and bad.
Summit
This is what Hell looks like when it's finally frozen over. Good for approaching with Ness' hyphen and reversed hyphen smash. However, those clouds that float on by aren't ever around when you need them the most. Your attempts of making it back are very slim.
Norfair
I still have yet to know what makes this stage so good for Ness. I never go here. I'd assume it's the platforms you can go through. I'm positive that most will secretly pull a uair under the very bottom platform. It's simply good for PK Thunder.
Temple
This stage was made for happy campers. It's not like you'll fight on this stage in competitive play, but look for unique ways to avoid your opponents if you ever come across this ridiculously big stage.
Mario Circuit
No worries of having to safely recover. That's all I see this stage being good for. Other than starting fires on the racers, I can't see this stage being very useful or bad for Ness.
Frigate Orpheon
This is not one of Ness' best stages. I've been here a few times to know why. I can't tell you why, but there is a reason. Just go there yourself and you'll eventually see what happens. Just be sure you're not here when fighting actual players if you plan on trying to figure out the issues of this stage for Ness.
Distant Planet
This stage is actually pretty good for Ness. The gimping is literally one sided, unless of course you get that creature to come by, then you're pretty much safe. Just avoid getting eaten. The only problem I have with this stage for Ness are those circular shaped items that grow. They're very annoying for PK Thunder if you're wanting to use it in the air. Of course you can probably get gimped by one of those if another player throws it at you.
Mushroomy Kingdom
It's a nice stage, but seriously, nothing good comes out of it. You can get in some easy kills, but anyone can do that. The underworld is the same way. Of course you can just be on the very top and u-throw your opponents to death. It's funny to do that, though. Just be sure you're not the one getting thrown.
Port Town - Aero Dive
This is my favorite banned stage. You can basically apply what I said about the Halberd with this one.
Final Destination
This is a great stage for Ness because of the open area you've got. Of course I hate this stage because it has big fat lips that kill.
Mario Bros.
Lame idea. This is anybodies game.
Green Hill Zone
Good for open aerial combat, but I hate the stage anyway. The platforms that break below aren't good for Ness' recovery. Plus you're on a half pipe the majority of the time. I hate this stage with a passion.
Luigi's Mansion
Good for fire wood, camping outdoors and other random stuff. Bad for PK Thunder, though. It's a good stage for Ness, but it's not his best.
Spear Pillar
I believe this ones got tiny lips. But it's good for hyphen and reversed hyphen smashes as it can hit your opponent a bit easier if you're under the stage. You can also surprise your opponents with PK Jibaku under the stage. That is if you can get your PK Thunder to hit you. Yes, this is possible. The area above is pretty good for Ness to fight on, too.
75m
Good idea and a bad idea. This stage is good for Ness, I guess. PK Thunder wherever and whenever.
Flat Zone 2
I liked the first one better. The stage is pretty much open to all sorts of attacks you can use with Ness. It's a good stage for him, I suppose, but there are many things that get in the way.
Jungle Japes
I have no problem with this stage to be honest. It's pretty open and the water can save you if you **** up your PK Thunder. Of course I wouldn't rely on the water too much.
Green Greens
Ask another Ness main that goes here often. I haven't had too much problems with this stage. Good for PK Fire against the blocks. It's good especially if they have bombs.
Pokémon Stadium
Again, this stage isn't bad for Ness. But it's not bad for just about any character, anyway. Figure out different things about the phases of this stage that you can use to your advantage.
Big Blue
I'm a fan of F-Zero, but not this stage. You're better off not using any PK attacks since I guess an opponent can move against you and you slide off to oblivion. Bet you never thought about doing that before.
Hanenbow
I don't think they were thinking when they made this craptacular stage.
Pirate Ship
You're worry free of using PK Thunder to recover! And you can water spike your opponents, too!