Twilight Princess is an excellent swansong for the Gamecube.
This is a much darker game than Ocarina of Time, and if this game came out for the N64 with Ocarina of Time graphics, I would say it was a much better game too. Ocarina blew me away when I first played it, and Twilight Princess didn't exactly do that, I still had a blast and think it's a much technically better game. Ocarina of Time was such a ground breaking game in terms of gameplay and graphics, so it would be hard to rate this higher though.
----------Battle System----------
The Zelda series has changed very little since Ocarina of Time, so Twilight Princess is no exception. While each Zelda has had a make over in turns of style, location, art, etc, the core battle system is usually the same. This is hardly a bad thing though, you stick with what's good.
The Zelda formula is pretty basic, you wonder around, watch a cutscene, find a new area, fight some monsters, open a new dungeon, get a new weapon and use it to advance through the dungeon and fight the boss and then you repeat this 8 times.
Link can transform into a wolf pretty early in the game, when after about 3 dungeons he'll have full control of him and use him for puzzles. When Link is in wolf form he can dig holes, track sent, kill Poes, and reach areas Elf Link wouldn't be able to reach.
There's a ton of new items to gain, like the chain ball, the spinning gear, the water bomb, and plenty of others. The dungeons are pretty long, probably longer than Windwaker's.
There's plenty of sidequests to do in this game, but I thought there was less of them than Windwaker. In Windwaker there was mini-dungeons, and just a ton of secrets to find on each island. I didn't find as much in this one, but in this game you need 5 heart pieces to gain a new heart, which makes for more hearts to find. They brought back the Poes to this game, but they're much easier to kill.
----------Characters / Story----------
You play as Link once again, you're a swordsman in training and a goat herder by trade. As some neighborhood kids are playing around chasing monkeys in caves, one of them gets lost, so Link finds himself on a little mission to save this little kid. After you save the kid, you go back to life as normal. Then on the next day Link and his friend Ilia get attacked by monsters. Ilia gets kidnapped and Link gets turned into a wolf and sent into a dark realm. As the land starts to turn dark, it's Link's quest to save the world.
This is probably the most complex or expansive storyline for a Zelda game, there isn't just one gold like the others.. like gather the triforce and then that's it. I loved the story, and the characters were awesome as well, although most of them were extremely weird.
----------Graphics----------
The character models look excellent, the lighting of the game has a ton of style to it. The monsters are creative, the areas are HUGE and I had no trouble with framerates or anything. The only problem is the textures can be a little dated at times.
----------Sound----------
Amazing music as usually. There's still no voice acting, but there are personalized voice clips for each character no matter how small their lines are, including animals. The voice clips are similar to what Wind Waker did, but much better in execution and quantity.
----------World Map----------
The world map about the same as any modern Zelda title. You'll find towns, talk to NPC, find secrets within mountain walls,etc etc etc. The world is sectioned off into various areas, mostly because of it's massive size. This is easily the biggest Zelda yet and I have no complaints about that.
You'll gain Epona pretty early in the game, and you can call her if you're stranded by blowing on a Horseshoe shaped plant. Eventually you'll meet dark monsters that fall from the sky, and you'll always have to kill them off at the same time. When you kill them, they leave their warp open, and you can then turn into your wolf form and warp to any of those spots for quicker transportation.
----------Time to Complete Game----------
39:49
That doesn't include the hour or so fighting the final boss and watching the endings and credits. I missed out on 4 hearts (19 heart pieces), I only found 33 Poes, I didn't get the biggest quiver, or wallet, and I didn't fish at all. There was a few other things I didn't do, but for the most part, if I saw a sidequest I would take it. So this is probably the biggest Zelda ever made.