Allow me to begin by quoting myself from a thread in the Pac-Man character boards:
Against

, Galaga ship (?), Bell, and Key will beat ALL of DH's projectiles, letting you get in on him. Every Fruit between Cherry & Melon, however, lose to all of DH's projectiles.
Your namesake, Galaxian, is what you'll want to charge up to, at least, for....
Another quote from myself in another thread in the Pac-Man boards regarding this MU from DH's perspective:
Perhaps

has what it takes? Any fruit between Cherry and Melon are going to be blocked by the dog's Gunmen, Cans, and Clays. Said blocked Fruit will also be up for grabs once it collides with your arsenal, especially Gunmen, due to its quick & low endlag. Do note that you'll have to dash or air attack it to pick it up, otherwise said blocked Fruit will still hit you. However, as soon as Pac-Man reaches Galaxian Ship (?), consider your projectile shields ripe for piercing. Hydrants knocked your way will also pierce your entire arsenal. The water from Hydrants will simply pass through your arsenal without messing with any of them.
If you DO catch a Fruit, you can try to hold on to it as long as you can to deny him the ability to throw any more Fruits. Of course, by doing so, you'll also deny yourself the ability to use any A button attacks (including Smashes!) and grabs as well. As the canine, your overall mobility is pretty good (you can even crawl & wall-jump!), and you'll still get to chuck Cans, Gunmen, and especially Clays. These will become your main sources of damage dealing if you decide to hold on the Fruit, because without his Fruit, he'll likely try to approach you, especially once he sends the Hydrant flying your way. Hitting him out of Power Pellet before he eats it by hitting the Pellet itself will allow you a chance to heal yourself a bit from the Pellet he drops. If you're still holding on to a Fruit when you try to go pick up the Pellet, you may have to throw it away in order to heal yourself with the Pellet. If there's a way to pick up the Pellet without having to throw away the Fruit first, please let me know. Trampoline will beat your Can, which is one way he'll defend himself against your edgeguards. A DH without access to A moves & grabs (due to holding on to Fruit) will have to play a ranged game like Marth, and possibly even counter-camp.
And a quote from xzx from the same thread as the above quote from me that I liked:
Hey Splooshie Splashy, you can Z-drop the Bonus Fruit, then eat the Power Pellet, then regrab the Bonus Fruit.
If you really want to safely chuck any Fruit between Cherry & Melon, 1. KO the Gunmen, 2. Get past the Can, and 3. Be close enough for Clay to be too risky for the dog's comfort. Power Pellets are one option for accomplishing this, as are Trampolines, Hydrants, powershields, jumps, spotdodges, and rolls. As the above quote may imply, if the dog's carrying your Fruit, you're in trouble.
Definitely try to get in on him, since that's probably the hardest part of this MU for Pac. If the dog player's upclose game is any good, you'd better get ready for a slugfest with his FAirs (his longest range melee move), NAirs, FTilt, 6 frame DTilt, and 4 frame Jab. If/Once you do get in, in terms of sheer speed, however, you win, due to your generally faster A button moves, particularly your 4 frame FTilt, your seemingly spammable FAir (ala Luigi), and your low cooldown Dash Attack (which can push away Cans). Your KO moves are more reliable than his, and you can go deeper for the edgeguards against him than he can against you, even with wall-jumps off of walls, which the both of you are capable of.
Mario's a decent pick against the dog, but his recovery is not as good as Pac-Man's, and Cape is not as effective against his arsenal as it would be against other projectiles. This MU is not bad enough for a Pac-Man to switch to someone else. Pac's got more tools to approach than oh say Bowser & Ganondorf & King Dedede w/out customs, which you should be thankful for. If you REALLY want to switch to someone else despite this intel, I'd personally recommend
Bowser Jr.