Being as I've been listening to the soundtrack of this game so much recently, I figured I do a review on possibly one of the greatest Mario games of all time. It is for Gamecube but obviously you can play it on your Wii as well, and I think you can pick it up cheap secondhand anywhere.
But anyway, the story starts when Mario recieves a message from his beloved Princess Peach when she discovers a hidden treasure map from the far away town of Rogueport, a typical urban town with many secrets to hide. It's not as simple as this though, when Peach suddenly goes missing... And Mario, once again, has to save her. With the help of your first sidekick Goombella and smarty boffin Professor Frankly to help you find the treasure (aka the 7 Crystal Stars) of which unlocks the Thousand Year Door, where the treasure is hidden (hence the title of the game)! Mario and his trusty party members (your party grows bigger as you meet more and more people along the way) then begin their adventure with a mission to find the 7 Crystal Stars to reveal the treasure, but it won't be as easy as that, as Mario assumes Princess Peach is off searching for the treasure as well, when really she has been captured by the Secret Society of the X-Nauts...
So more on the game. It's one of the only Mario games styled as an RPG, but it's still extremely fun to play and the combat and fighting can be somewhat fun to start off with, yet get annoying when monsters constantly run into you to begin a fight. Boss battles can often leave you pulling your hair out and screaming at your TV screen (especially the final boss...), but the game is a good challenge and really enjoyable. Your party members often have special moves to help you in battle and you can switch them in and out like in Pokémon. What I personally find really cool is when you enter a battle (either by a monster running into you or you jumping/hitting the monster), you'll run onto a little stage, with a small audience of typical Mario monsters (eg: Goombas, Koopas), which can be sometimes funny as they'll throw items to you randomly or scream and run out the room. Another thing to note, is when you collect Crystal Stars they'll activate a special power you can use in battle, of which are very powerful (Eg: Art Attack, where you draw round your enemies in circles of which inflict damage), of which is cool. And of course, you'll win "star points" at the end of each battle, and when you get enough star points, you'll level up and you'll manage to add more HP/FP etc etc.
As mentioned in the title, this game is called "Paper Mario", so it is styled all in 2D. Mario can gain abilities of which he can turn into a paper plane, for example, to help him cross difficult paths of which you can't just run through. This gives the game to have lots of hidden secrets you can't normally find and makes the game more fun just by exploring to find treasure chests and etc. You can find loads of hidden secrets, of which you'll often need to find to help you advance onto the next part of the game.
Now, onto characters. There are 6 characters for you to add to your party and an unlockable/optional character as well (of whom you'll often encounter a few times throughout the game), and as said before, they all have unique moves in battle and throughout the game itself. You'll often find it difficult starting off with just your one character, but it gets more fun battling and bonding with these new characters throughout the whole game. What I also love with this game (and all Mario games in general), is that, they can just chuck in, totally random, quirky little characters of whom clash and you'd never expect to be together, yet get away with it so well and seems so normal. It's not like you can throw in a mysterious-looking ghost with a nerdy-like goomba into, let's say, a Legend of Zelda game. And that's what I love. The characters (and even those not in your party) say funny little lines, and of course, you have your stereotypical personalities as well (eg: A gangster Koopa. Who would have ever thought of that?!).
The levels as well are so well planned out and thought through. Each little detail defines the place so well and the little stories that go along with it are somewhat fun to play with (eg: A detective's mystery on a train to Poshley Heights). Everything is so stereotypical, from your gothic, emo dark town to an elegant, posh town where everything is ever so perfect, even the characters that roam around there. The soundtracks that play set the mood ever so well and the houses and locations you can head to are so well set and thought out, it must have taken Nintendo ages to create this game. Even when you have completed the game, there is still so much for you to do and explore, so you'll never get fully bored of it.

Mario and Hooktail, one of the bosses.
Little extra fun things to do within the game:
You can visit a Toad chef when in Rogueport, of whom you can give any leftover items and he'll mix it all up into a recipe for you (of which you can use during battle).
Hotels you can visit to help replenish health, but you'll need some coins to be able to stay there though!
The Pit of 100 trials where you can battle any kinds of monsters to help you level up (but be careful, it's really difficult to pass them all)!
Listening to Luigi's tales of the Waffle Kingdom... Yawn...
Little extras in this game really add up to make this game unique in so many ways. It's possibly one of the best Mario games I've ever played, yet it is challenging and sometimes running into monsters can certainly get annoying when playing it. However, this doesn't even seem to knock the game down at all. It's fun, it's bright, it's cheery and it's Mario! Of course it's going to be crazy, wacky and insane, but being able to embark on a quest in a paper world with little punies and floating cities in the sky is truly amazing. This game is amazing. If you're sitting there, bored, don't know what to play...
PLAY THIS GAME. It's so addictive and when you start playing you cannot stop.
So of course, this game is going to receive a huge thumbs up from me, now that's left for you to do, is to play it!
4.5 stars out of 5.

Go Mario, go!