ModNation Racers is the best kart racer ever made, and you can create & share characters, karts, and even tracks.
Let's start with the Career mode. Not only is it surprisingly lengthy, and has a little bit of story to it (which can be mildly entertaining, but the races have tons of replay value. There are multiple challenges to complete on each one; beating these challenges unlocks extra vehicles and body parts for the Creation center, as well as some full characters (called Mods) and karts. The Career mode tracks also have special tokens that you can pick up, that unlock even more Mods, Mod parts, vehicles, and vehicle parts.
At the Creation center, you can create your own Mods, karts, and even tracks. The creation tools are excellent! They're extremely simple and easy to use, but you still get an amazing amount of options, and can create stickers to attach to your karts. The only real downside is, many of the parts either have to be unlocked, or must be purchased as DLC. Still, this is a very minor nitpick, since you have tons of options available at the start. When creating tracks, you can choose the backdrop & time of day. To create the track, you drive a vehicle that leaves track behind as it drives along; you can adjust the elevation of the track while driving.
The online community in the game is also excellent. When searching for content to download, you select the category, and the content is listed in order of highest-rated (you can rate content on a 5-star scale). You can play with any of the Mods, karts, or tracks that you download. As a result, you'll always have more tracks to download and play, so there's always something to do (other than just racing against other people online). The main hub, the ModSpot, also has the highest-rated content (for the past week or so, I think) shown right on display. It's also easy to connect with other players to race with them, and there are tons of options & modes for racing online. If you create a private race for friends, you get more options for customizing the race settings. You can also do the same thing if you race with friends in co-op. Unfortunately, as far as I can tell, you cannot split the racers into two different teams, like you can in Mario Kart DS or Wii, which is disappointing.
However, all of the options, modes, and customization in the world would be useless if the gameplay sucked. Thankfully, ModNation Racers succeeds there, too. It doesn't just set the status quo; it obliterates it, becoming the brand new standard that kart racers should be judged by. It's not just a shameless Mario Kart ripoff (cough, Sonic & Sega All-Stars Racing, cough). It features a surprising amount of strategy. First of all, the weapons are a lot more balanced, and require more strategy. Similar to Mario Kart, you drive into an item box to pick up a weapon that can be used against other racers. However, unlike Mario Kart, there are 3 types of weapons you can pick up, but each one has 3 different levels. Picking up an extra item box upgrades your weapon to the next level. For example, if you pick up a rocket (Level 1), but then pick up an extra item box, then you will gain homing rockets (Level 2). Level 3 gives you a storm of rockets that attack everyone in front of you. This adds a ton of strategy, because you have to choose between using your weapon right away, or waiting until you get a much better version of that weapon. Remember: if somebody attacks you, sideswipes you (yes, you can sideswipe people), or you fall into a chasm, then your weapon will go down by one level (if you're at Level 1, then you'll lose your weapon). Also, there is a special meter on the side of screen, which can you fill up by drifting, performing tricks, etc. You can use up the energy in your meter, either to project a shield that protects you from oncoming attacks, or to give yourself a boost in speed. This forces you to do more than simply drive around the track, and it forces you to choose between giving yourself a speed boost or protecting yourself from other racers' weapons. Just like the rest of the gameplay, the controls are easy to use, but challenging to master.
Even the game's presentation is great. The game has a really cool cartoony style that actually feels original. The characters sort of have a bobble-head look, to them. The cutscenes between races in the Career mode are extremely well done, and the characters' personalities are expressed very well. Unfortunately, the music is nothing special, and you'll tire of it quickly.
There are some places where some people might feel like ModNation Racers is lacking, but these are VERY few. It's rare to have a game with this much content, and this much polish, at the same time. I'll even go as far to say that it's one of the best games I've ever played. There's plenty of online racing options, but even if you're not into online racing, you'll still have tons of fun and play time by playing through the Career, racing on tracks created by other people (as well as creating your own), and playing with your friends in the living room via splitscreen.
This game has been out for almost a year, so it's pretty cheap by now. In fact, I got it for $30. So what are you waiting for, kart-racing fans? Buy this game!