interesting points brought up...
the way i see gw players can chose to play very defensive or very offensive in a lot of matchups, he has the flexibility in his playstyle to do so.
defensive -
since ness has no *quick* projectiles to bother a gw player with at mid to long range, he can certainly play a defensive style against ness. Thus we would look at ness's general approaches. Dash attack has been mentioned quite a few times, which isn't a bad move by any means, but doesn't really break gw's defense. If ness is dashing at gw, its likely he will dash attack, sliding upsmash, or grab. In gw's retaliation, dtilt beats upsmash and grab of course, shielding beats dash attack and upsmash, and either rolling back or up b'ing out of shield will beat grab as well.
thus we move to his air game. fair seems to be the only real approaching aerial, and if gw is chilling on the ground, up b out of shield is certainly capable of beating this, although I imagine that its possible to space this move to avoid getting grabbed against shields. I can also see the dtilt beating the fair when ness is approaching because it hits so high.
overall i see no really good ways to punish a defensive gw. nothing really sheild eating like snakes cc game, no frame traps like mk/marths dtilts, no quick projectiles that can't be absorbed, and no quick/uncommitted outrange'ing moves (once you dash attack you'll be closer to gw than you'd like to be to continue pressuring).
offensive -
if the gw plays offensive, then there are a lot of things that ness has to deal with. Gw players will usually approach with turtle, nair behind sheild (or even in front in ness's case), spaced dtilts, key behind sheild sometimes, and these are just a few approaches that i can think of that ness really can't deal with.
☼ turtle - if the gw player sh's a turtle and ness is trying to be defensive, he has choices of sheilding or trying to attack it with a fair. We've already covered that the turtle will beat the fair. Thus they either have to shield it fully and move away, or try to dash/walk away and punish. Since ness has no long range attacks to do this, he either has to move out of the way or sheild it thats it.
☼ nair - works similiar to the turtle, just with less range and less lag. Ness has no oos options thus would have to attack this with a fair. Gw will probably be watching for this (its the only real approaching move ness has in the air), and can either back off or just air dodge through and grab to punish.
☼ dtilt - no projectiles or grounded range attacks. gw can simply walk near the ness player and start spamming to pressure his sheild. If he tries to go into the air the dtilt will catch him. He can really only roll away and regroup.
☼ key - if landed behind the shield i don't think ness can turn around and grab fast enough. the only times that this approach doesn't work for gw that well is when either the character has a move that will outprioritize it (upsmash might, but since that is a tricky timing situation, slowfalling would certainly be an option to get by that) or they have a very fast grab/oos shield option. Ness doesn't really have either of these, thus its probably another safe approach.
Well that covers offensive options, most of which force ness to move away, he has little to combat gw's range.
Overall gw's combos will be much better and rack up much more damage, not to mention they are easier to land. Ness has no answer to up air spamming, which he would drastically need to avoid nair combo'ing along w/ a high priority/range dair (none to be found). He has no combo interrupters (nair might work if it had more range).
Offstage when ness is recovering, all gw really has to do is wait. If ness is looking to use his dj to get back from below (slowfall key works nicely) and from the side (dtilt beats both fair and just him trying to grab the edge). If gw sees the ness start the up b sequence, a fair will knock him out of this easily. If he's too far away for that, its likely that he needs to grab the edge, which a hog solves. If you are too far into the stage to do anything, grab the ledge and use the up air to get a smash off and punish.
When gw is recovering, he goes low, and ness has really nothing he can use to interrupt him, fair will block a pkt, which is the only thing i can see ness using to edgeguard.
Ness's spike killing at 0 is a pretty moot point, unless he has a guaranteed combo to go with it ( i have yet to see anyone bring one up, thus i'll assume it doesn't exist) or it could be used to effectively edgeguard, both of which don't seem to be options.
Ness's kill moves are: fsmash, bair, bthrow, upair, dair. Fsmash is certainly much too slow to really do anything, bair would be nice if it beat any of gw's approaches, bthrow is legit (kills early, might be his only reliable kill), upair/dair don't have enough range or priority in any situation to hit gw.
Gw as you know has a lot of kill moves, all of his smashes (most of which are safe on block v ness because has no ground range), and fair (only ness's fair will beat it), and bucket (can be used out of grab release or in a lot of other situations). Most of these are reasonable to land vs ness due to his lack or range.
So what have we covered?
Ness can approach gw ok, seems more like a stalemate due to his lack of projectiles.
Ness can't do very much at all vs gw's approaches, he has to run away.
Ness can't edgeguard gw at all.
Gw will likely destroy ness off the stage
Gw can combo ness well (dthrow setups are nice, ness has no answer for up air/nair, no combo breakers)
Ness can really only kill with his bthrow.
Gw has a lot more options to kill.
How is this not a 7/3? again unless i have a lot of major flaws in my argument, i see no reason this shouldn't be rated as stated.