Only trouble with Pikachu i have is G&W, Lucas, Wolf, and Olimar. I have yet to fight a good Ness with Pikachu.
Mario just counters a campy Pikachu. but Pikachu has more priority then Mario and his projectile out spams his. It's not hard to aggro Mario.
Marth vs Pika, Marth has more range in general ok stop debating this. Marth is LIGHT though Pika is lighter, doesn't mean Pika can't kill Marth fast either. The only problem is Marth's range in his aerials over Pikachu's. But fair is punishable now and bair is slow compared to Marth's other attacks. Also pikachu does have QAC.
Wolf's range > Pikachu's range and his shine stops Pikachu from attempting to grab him. (I mean against good wolves who know how to play, not spammers)
Pika vs Rob, i believe 50/50. Rob's aerials kill, but are slow. Pika's aerials are faster so timing is key. Either attack before his come out or punish after he attacks. CAREFUL with nair, its tricky at first. Gyro stops jolts 50% of the time, (meaning Jolt goes into it OR over it) lot of Robs throw one out to stop you come camping. Using gyro against him is fun, and glide tossing is also fun xD. Watch out when he does it though. Don't spam thunder or jolt on the ground (who does..?) cause side B will reflect it at you. Thunder only when Rob is in hit stun cause his side B has start up lag.
>.> am I the only one who has trouble against G&W? His bair stops anything i do.