If it's strictly a character v. character question, with hypothetically identical players on either side, who each have a healthy working knowledge of their opponent's character, then yes of course Ness has the advantage. Ness has the KO power to knock out Luc before ludicrous aura kicks in, has the psi magnet to limit the use of AS (and FP to an extent), has a solid neutral to rack up to KO%s and has a perfectly fine recovery.
Okay.
Now that we've established that the Ness character is well equipped to give our Lucario a hard time, does Ness having this advantage based on the available tools mean we shelve Lucario at the first sign of a Ness ala:
How I deal with the ness matchup:
Take character select token off of lucario
Move it to sheik
or do we find other ways to confront the matchup?
Obviously this is a question that each of us will have a different answer for. Some of us won't want to deal with the stress and strain and pick someone else (I myself will flat-out refuse to use Lucario against exceptionally good Link players, for instance, but that's a discussion for another MU thread). Others will find ways around the disadvantages and work with that.
In the Ness example for instance, one of the broader strategic choices I often make is to condition the opponent, encouraging them to make use of psi magnet. The usual way I condition the Ness player in this way is to fire several Aura Spheres when it is reasonably safe to do so: literal spamming. There have been occasions where I have fired off fully charged spheres vaguely in the opponent's direction, which I had no intent to hit, simply to plant and encourage the thought in my opponent's mind that I'm a dim-witted projectile-spamming moron who likes to use AS too much.
Somewhere in there is about when the other guy starts getting real friendly with their projectile countermeasure. It often, but not always, happens after I've accumulated a fair bit of aura on Lucario (though not much damage on the other guy), when the opponent is thinking about KO options, and when they start to think I'm really not that good a player. That's when they usually start taking me less seriously as an opponent, and slip into patterns as they put up countermeasures, and when I start reading their moves and predicting like a boss.
Once I can read and accurately predict, supposed match-up numbers mean very little. The real trick lies in finding ways to draw out specific reactions, remember and prepare for them, and all while playing your own cards close to the vest as not to have the same happen to you.
Granted, truly skilled Ness players just won't fall for these kind of strategic mental shenanigans at all: they will be reading and predicting
you instead, like just about every really good player does. Personally though, when I'm up against skill of that caliber, it rarely makes much of a difference which character either of us is using: If I'm getting significantly out-played, I really don't feel there is much that changing characters can do for me: I will still be out-played regardless. Similarly if I feel like I'm really closely even with someone skill-wise in battle, with a few notable exceptions, I have such a level of comfort and familiarity using Lucario that picking any other character feels like it could be a step down in my level of play. That, or it's just a sign that I need to step-up my practice with my other characters.
laying safe and getting in and out while racking up damage 
