Let my post my rankings from a previous thread, and then give detailed explanations:
1. Luffy
2. Zoro
3. Sanji
4. Franky
5. Robin
6. Chopper
7. Brooke
8. Nami
9. Ussop
1) Should be self explanatory. Luffy with Gear 2 is far beyond Zoro, without gears (or even with gear 3) they are almost incomparably close. Gear 2 is still a far greater "form" than Zoro's Asura though, but without those forms it would almost be impossible to see a difference between their strength levels.
2) Zoro should also be self explanatory. Always comparable to Luffy's strength, their only comparison was back at the start of grand line when they were equal, and they're growth has almost (albeit the gears mentioned earlier) been equal.
3) Sanji rounds off the "Monster Trio". Always seen as close to Zoro and in competition, but never so much with Luffy in particular. Sanji's Diable form upgraded his power, but his speed and damage output is lower than Luffy and Zoro respectively.
4) Franky, in my opinion, is far closer to Sanji than many actually see. Sure he's taken a beating from Pacifistas, Oars and what not, but we're talking about a man made of metal with, quite possibly, one of the strongest attacks of the SH crew in his Coup de Vent. I don't see an enormous gap between Franky and Sanji, I couldn't honestly pick a winner, but since Sanji has a bigger fanbase than Franky I'm sure you could all tell me who the winner would be.
5) Robin is, by all of you, underrated. You all say "oh man she can't topple castles or outrun a speeding bullet", and this is all true, but her ability is still broken. To date, the only time I've seen her struggle is really against Moria, whose abilities allowed him to outmanouvre her clutch. If she was fighting Zoro, she could grab his arms and pin him down. If it was Sanji, pin his legs. If it was Franky, squash his balls. If it was Luffy...well she'd probably just stretch him a little. And then I see stuff like "Well someone strong could stop her from doing stuff" and all I really should have to do is point to how many arms she made to hold Moria (a "giant" human...thing...) in place. If it was also simply a battle of strength, you're basically saying everyone she's defeated (Pell, fat Skypeia guy, etc) are comparable to Ussop in strength or something ludicrous.
6) Chopper has always been the middle of the gang, and he will stay here. I remain unimpressed by Monster Point given the obvious lack of control and any discernable traits other than "growing huge", in which case he's basically a Gear 3 Chopper without a brain. That said, his other points are still very useful, and his damage on Oars with Arm Point was insane. Multi-talented, but still has a lot of room to grow.
7) Brooke is overrated by everyone on the other hand because he has a sword I imagine. Apparantly swords = better than people without swords except Luffy? Brooke is fast, sure. He has some good technical skill, sure. However, we've been shown that his stamina is low (running on water tires him out fast), he is super fragile (all damage breaks his bones, he has no "cushioning") and his damage output is not remarkable in any way. When you throw in his music he appears to have more combat ability, but everyone I've ranked above him should be able to pick him apart quite easily.
8) Nami is above Ussop, but some are blinded by the fact that Ussop finally won a battle in the Thriller Park arc. Nami has three elements which allow illusions, AoE damage, control over local weather, targetted damage and defensive measures. Nami was also, by Oda, ranked as one of the smartest people in the East Blue, and is still one of the smartest in the Strawhats (behind Robin nowdays though). She's still pretty much a "normal" human, yet has managed to take out some, typically, strong enemies since the introduction of her Climatact. Of course, she's only female, and japanese Shonen ranks females as about 10x weaker than males for some reason.
9) But then we have Ussop. He is unremarkable in every way except that he has a fair amount of sniping skill, comes up with some nice inventions, and is an incurable liar. He is the most basic "normal human" in existence. When he gets hit, bones break like they should. When he runs, he doesn't disappear faster than eyes can follow. When pitted against his own crew, Ussop might be remarkable in exploiting their weaknesses. However, Ussop still remains the SH with the lowest damage output and least amount of "wins" uner his belt. I can see he has grown since Enies Lobby, but only to somewhat catch the lower tier Strawhat's who he had, very quickly, been falling behind. Oda will never make anyone in the crew weaker than Ussop, it's what makes his character.
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Ok that was a long bit of typing, just thought I'd get it out there. Too much overrating Monster Trio and other favourite characters out there.