I'd say Fox has the advantage (but not online with 3 or more frames of delay)
Fox can play defensive all he wants with lasers, attacking in whenever he feels like there is an opening. It's easier for Fox to attack/defend against Mario with superior movement, containment with lasers, and overall more versatile moves. His speed is also 2nd highest in the game, just 2nd to that of Falcon (also Fox's initial dash is faster)
Fox's lasers absolutely take a dump on Mario's fireballs in terms of usefulness in this matchup. Fireballs can be killed by any aerial, even a jab (i think) and can be jump-canceled reflectored.
Fox to me also combos Mario just as well, if not slightly better, against Mario. A simple starter is down-tilt to up-air(s) to a "finisher" aerial like n-air or you can smack him around onto a platform for even more molestation by fox. Both dreamland and Hyrule have these platforms and the **** house so Fox really doesn't have to work his *** off to combo well. Just cuz Fox in Melee takes the most technical skill doesn't mean he has the disadvantage against Shiek (sorry Melee haters)
You can also be lame and do many up-tilts while walking to compensate for slight horizontal movement
or in hyrule **** tent you have a rather easy 0 to death on mario (so does Mario, sorta). Fox also can be really lame and abuse ledge invincibility to keep Mario off with throws and stuff.
If you "shove" him off with a forward-air hit at a lower percentage, you can reflector Mario to send him down. Mario is then forced to recover awkwardly onto the stage without fireball support where he then is subject to further foots up the butt. If Mario tries to down-b you can reflector him again
If you are on the middle area on Hyrule or Dreamland stage, Mario simply can't run fast enough to tech chase him if Fox rolls away (and there's space to roll).
And to be honest, Fox doesn't really need his drill to combo most characters anyways unless they cannot DI.
Fox's recovery has also a really big misconception as a terrible recovery (kind ofbad but not **** like Falcon's). If you recover high you have enough horizontal movement to juke effectively and live.
The factors against Fox:
Mario's recovery is better but still punishable
He is bound to get ***** if he is thrown off stage or gets into an down air- up air set up to perfect up-airs to up -smash. It's actually impossible to escape down-air to up-air with Di since the 10 slow hits let Mario players follow the players DI or stun lock most for the Mario to simply turn around and grab or whatever since Mario's down air ends rather late for the other player to respond (especially with Falcon)
Basically I am saying a horrible mistake by the Fox player whether it is lag induced or by their own mistake leads to problems for Fox players. We are assuming higher level play however, where experienced Fox players do not simply jump into their doom (often).
It's a big baiting game between Fox and Mario. Mario can park himself next to the ledge, duck lasers, dash dance, but Fox has the tools necessary to take out Mario players who do this (and anything). A mario player who tries to approach is already put in a disadvantage since Fox can manuever decently as well.
+ for Fox against Mario. Just a small advantage that good mario players can overcome if they are better than the Fox player.
If you play online, you'll find that Fox gets worse exponentially with Delay, making Fox make much more mistakes and get owned. If this was a matchup thread based on online, I would place Fox as = or - against Mario.
My experiences against talented Mario players in RL, however, tell me otherwise
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Luigi is a crappier version of Mario. His higher short-hop in comparison to Mario lets anybody get out of his down-air to up-air combo unless Luigi does this move late into the short-hop.
Luigi is slower, slippery, and fireballs, while still useful in certain times, are worse than Mario's and thus lack even more use.
Fox molests Luigi even more so than Mario for these reasons. There is still some gimp risk of course but Fox nevertheless has an easier time against Luigi since he is basically a weaker, slower mario. His "better-version" of moves don't make up for his slowness.
Fox ++ over Luigi
Fox vs Ness
Ness has trouble approaching like crazy. Any decent player can also read his double-jump speed up aerial also. Ness has better priority aerials but they don't mean much if they cannot hit. Ness is gimped very easily also. You'd think his down-b could be used to stop the tide of lasers but down-b has a slight start up and cancel which Fox players can abuse.
Fox has great combos on Ness, great gimp game like the rest of the cast on Ness, lasers, speed, etc.
Fox's jab can tie with every up-tilt in the game except Kirby's and maybe (DK ? ). Thus, if Ness is an up-tilt *****, you can either trick him by doing an aerial but not making contact before moving in with up-air, throw, etc or simply jab his up-tilt. Fox's recovery time is slightly faster and in 90% of cases, most Ness players won't expect it and/or won't react fast enough for your punishment.
Ness players really rely on the mistakes of Fox to get hit by up-tilt, up-air, down-air to get their combo flow going. Fox simply can't jump onto Ness with an aerial and expect good results. A throw off the stage is often death for Fox as well.
Fox + over Ness.
