Yep, been meaning to do one on this too, since it's been bugging me lately. Meaning as of last night, I decided to put Okami into the PS2 again cus I wanted a break from the (almost beaten) Persona 4. It's like every time I put in Okami, I remember why it's never there for more than one sitting, and even then it's only in there for less than 3 hours. Basically, I think I've finally figured it out, I friggin HATE Okami, it's the only explination for why I wished I was playing Sly Cooper the entire time and now I've just decided to give up on Okami and replay Klonoa, or Sly Cooper, or the PS1 Spyro games or something less horrible. Maybe I'd enjoy Kung Fu Panda more, but I don't particularly care to play it either,so never mind. So, as I played I tried to think "Ok, what is so bad about Okami that Legend of Zelda Twilight Princess and Sly Cooper did right?". Anyway, I'm going to sell Okami at my next convenience.
First, graphics. Okami has pretty good graphics, but while they're unique, I don't think they're highly functional. It should best be compared to other cel shaded games here and not Twilight Princess, so I'll go with Wind Waker, Sly Cooper, and Klonoa. Klonoa has simple graphics, but the colors are so bright and the backgrounds so rich that it just puts Okami to shame. Wind Waker is a bit more stylized (what with the bomb clouds), but the style never makes it feel like you're not playing a Zelda game (once you've gotten past the first 20 minutes anyway). Then Sly Cooper, which was probably the least graphically impressive of the group, but like I said, the whole thing functioned and it actually acheived (for me at least) the comic-cartoon feel a lot better than Okami got its living picture feel
Sound, although I really mean voice acting. Here's the best opportunity for Klonoa to be compared as they both use non-existant language in a type of gibberish speech. But in Klonoa, you could actually pick up on words having distinct meanings, it wasn't actually as random as it seemed and I rate it highly among fakie languages used for games. Okami was just a bunch of Animal Crossing-esque gibberish junk that had pretty much no emotion. Once again, a game at least 4 years older putting Okami to shame.
Gameplay style is a huge biggie, this includes exploring worlds, doing things of actual importance, etc. Here I'm going to pick Jak & Daxter and Zelda Twilight Princess. For Jak & Daxter comparison, I mean world exploration. Okami practically shoves exactly what and how to do it in front of your face, Jak & Daxter says "see, power cell. but I won't tell you more, have fun, bye!". Okami was way too easy in that sense, not to mention all the random items you'd find in those stupid chests, at least the precursor orbs were useful. For dungeon exploration and fights I compare to Twilight Princess. Pretty much all of the enemies in Okami were easily defeated bore fests. Granted, the eyes or the tail are always the weaknesses in Zelda which isn't original either, but it gives you a better sense of accomplishment at the same time. And the dungeons in Okami are pretty linear in that if you just follow around, you'll end up at the boss. Zelda requires you to look at one room, then another, and figure out how to connect a bigger picture, making for epic fun dungeons (except for the water temples, obviously, and perhaps SnowHead in TP)
To conclude, I hate Okami, it's overrated as heck, and if you can't find a better PS2 platformer for 1/4 of the price, you aren't looking for one. I can name at least 10 action/adventure platforming or action RPG games off the top of my head not even including sequels: Klonoa, Sly Cooper, Jak & Daxter, Zelda, Ape Escape, Dual Hearts, Kingdom Hearts, Tales games, Alundra, Astro Boy: Omega Factor. Go play those instead, except for Alundra, you can get them all at half the price of friggin Okami. I don't like overrated stuff.