in general an average OP character is just miles better than an average Naruto character
but Luffy is just so much better than Naruto, Naruto isn't even a good character, Kishi wanted him to be this sad kid who has always been pushed aside but actually he turns out to be the son of who is one of the biggest legends in the Shinobi world - the 4th hokage, represents the beast line named Senju (opposed to Sasuke's Uchiha line), has a mother from a clan feared enough that entire villages were destroyed because they were there (the Uzumaki), he is the child of prophecy and has an extremely powerful monster inside of him who was supposed to be a ruthless killing machine but turned out to be a great buddy, he just wanted to have some love ... hard worker my ass
not to mention Kishi wants Naruto to be Luffy and Goku funny ... but fails MISERABLY almost every time (for example a few chapters ago when he forgot Senjutsu works on Obito and made that face, it wasn't funny it was just ugly ... period)
Luffy is my fav character in his series, followed by the rest of SHs
Naruto isn't even near the top of my fav char's in his series, I like plenty of them more: Minato, Itachi, Jiraiya, Nagato, Tobirama, Hashirama, Kakashi, Kushina, Hiruzen, Orochimaru, ... and if things go the way they are going I'll prefer Sasuke soon as well
OP would suck without Luffy, Naruto would be better without Naruto (which is ironic because the series is named after him)
not to mention Naruto's flashbacks and speeches, many people bash on FT for it's friendship speeches and powerups but I think Naruto has both more annoying speeches and flashbacks as well as more ridiculous powerups and that's not even counting speeches and powerups of other characters (yes I'm looking at you Kabuto, Obito and Sasuke ... others as well)
that being said I love the Naruto manga (have for 7 years) but it's not because of it's main character