Hands down, one of the best Mario games of all time.
GAMEPLAY
The story in Super Paper Mario is that Princess Peach has once against kidnapped, but this time by a new villain Count Bleck. Peach is then forced to marry Bowser, the result of which creates a Chaos Heart which is said will destroy all worlds. Heavy stuff for a Mario game.
Most of the game is played from a traditional 2D view. Later in the game, Mario gets the ability to "flip" from 2D to 3D. This is the main feature of the game, and it works exceptionally well. This allows the game to have all sorts of unique puzzles and hidden items.
Some of the RPG elements from past Paper Mario games have been removed in favor of going to a more traditional platform style of gameplay. For example, gone are the turn-based battles of past games. Now enemies are battled and defeated in real-time. Most often by jumping on them. This might upset some long-time series fans, but overall I think this helps speed up the pace of the game.
Like past games, you can also control several other characters, and switch between them on the fly. Also new are the pixels. These characters assist Mario in his quest by giving him special abilities to overcome challenges and enemies.
The game is played by holding the remote sideways just like a NES controller. You use the D-pad to control Mario's movements. This works well, but I wish the game took more advantage of the Wii's motion sensitive controller. Instead it's just limited to pointing it at the screen to find hidden items, and shaking it to earn extra exp when stomping on enemies.
GRAPHICS
The graphics are undeniably sharp, and detailed. The unique visual style of the series is present, but better animated. It especially looks good in HD. Everything about the visual presentation oozes style. Because of the 2D and 3D nature of the game, you'll often find areas that allow you to go into the background to solve puzzles or find hidden areas.
The only downside to the visuals is that the levels look better in 2D than 3D. When flipping to 3D the levels tend to lose their visual style, and just look odd in spots. When you get a star your character transforms into a giant 8-bit version of themselves. This doesn't look very good, though. I'd wish they had stuck with the normal cartoon style for the characters in this mode.
SOUND
This is another area where Super Paper Mario shines. As you'd expect, the music is well done, and contains remixes of the classic tunes from Super Mario Bros. The sound effects also have the same style and appeal of the graphics. Which helps add to the lighthearted nature of the game. The only lacking area is that there are no voice-overs at all. Considering this is an RPG with a lot of text, it's not uncommon to have no voice-overs, but it's still a feature I find missing.
VALUE
On your first play it will probably take you about 15+ hours to beat the game. Most of that time will be spent reading character dialog, as there is an absolute ton of it. Plus with no way to skip a scene, it can be a chore to just get to the next level. This also makes it a pain to start a new game as it can easily take 20 minutes to wade through the opening scenes to get to the first level.
The main quest is great, and very entertaining. The dialog is well written, and there are some scenes in the game with are sure to become classics. The Bowser and Peach wedding comes to mind. There are also numerous side-quests, and once you beat the game you are given the option to go back to Flip-town, the main hub of the game. From there you can revisit levels to find secrets, and finish up side-quests.
Super Paper Mario is an instant classic. It moves away from the more traditional RPG elements from past games, but this is a good move. The game is very entertaining, and a blast to play. If you're even remotely interested in the Mario series, you owe it to yourself to pick this game up. You wont be disappointed.