Paper Mario: The Thousand-Year Door plays with the absurdity of the Mario formula in marvelous ways. It makes fun of itself relentlessly, yet still manages to be earnest when it matters, and the gameplay around which it's built takes the best elements of the Mario games' trademark simplicity, and constructs out of them a compelling, engrossing RPG. All the clichés present in it are thrown at you with the utmost cleverness, and the quality of the writing is typical for what Nintendo's localization team produces.
Basically, you'll actually want to talk to the myriad characters that populate the colorful worlds. Inane as what they have to say usually is, it's also often clever and funny. Maybe it has something to do with that Nintendo magic that everyone is always talking about, but there's definitely something here for everyone, even if they may normally think themselves above something so saccharine. Paper Mario: The Thousand-Year Door's combat system is pretty much where it's at. It doesn't really deviate too far from the conventions of console RPGs, but its execution is full of ingenuity and aplomb. If you've played the N64 original, then you'll know it well, as it hasn't changed a hell of a lot.
Basically, Mario and one of his companions are pitted against small groups of enemies, all in a turn a based scheme. Everyone takes turns beating on each other, with the dominant theme being timing: when Mario strikes his enemies with his hammer, for instance, you have to pull the analog stick back, and let it go just at just the right time, matching the moment of impact. This kind of precision is encouraged rather than strictly enforced, though. On top of all its elegant game design, Paper Mario: The Thousand-Year Door is also marvelous to behold. It's actually the first thing you'll notice about it. While the idea of superimposing 2D characters upon 3D environments is far from a new concept, this game does it with unrivaled virtuosity. Whole environments will often shift as you travel through them, giving you not only a moving sense of scale, but also gratuitously showcasing the simple, subtly crafted art used to make them come alive.
When it comes to Paper Mario: The Thousand-Year Door, it's mostly all good. If you have a history of playing 2D side-scrollers, this game will make you remember just why you loved them. And if you have a soul, then this game will make it feel all warm and fuzzy.