So I disagree.
1-Pein could use all elements, could absorb chakra, could control gravity and forces, had access to multiple summons, and enormous amount of chakra, and some of the most fearsome techniques the shinobi world has ever seen. (He can summon a monster that sucks souls and can bring dead people back to life. Saying Sasuke or Itachi could beat him is just ignorant. The Sharingan is good, don't get me wrong, but Pein's eyes are unmatched.
2- Pein didn't just lose to a loud mouthed kid. He completely wiped out Konoha and almost all their shinobi, and then fought Naruto in Sage mode and the Kyuubi. Naruto isn't as weak as you say. Despite him not having a large array of techniques, he still is very resourceful and is a host.
3- Yes Pein was played by Madara, but everyone and their mother is in the manga now (including Sasuke) He's very old and has access to a ridiculous space time ninjutsu. Madara isn't your average shinobi, he's without doubt a genius. Not to mention Pein was like only 30ish so Madara was much more experienced.