An exceptional fighting game in the vein of Super Smash Bros. that's only available on the DS.
Graphically, Jump Superstars is a pretty game. It sports some of the best 2D on the DS thus far, although it's not as if the game looks so good that it won't ever be surpassed in the graphics department on the system. Still, the game is an obvious big step up from most Game Boy Advance titles and really just looks so polished and nice as these characters battle in these manga inspired areas.
In terms of gameplay, Jump Superstars has a simple, yet effective battle system. In order to K.O. (knock out) your opponent, you will have two ways of doing so: either knocking them out of the battle area through a broken wall or by depleting their J-Soul. J-Soul is basically recognized as your common life meter. When you die, you drop these gold coins with the letter "P" on them, essentially the equivalent to how much power is left on your special gauge. Your special gauge determines how many more special attacks you can pull off before you have to replenish your power, either by constantly attacking your opponent or by picking up other gold coins. Gold coins can also be found in barrels and treasure chests in addition to fallen enemies.
Some people have compared Jump Superstars to the Super Smash Bros. series, and that would be a pretty accurate assessment. However, they're not quite similar in every category. Yes, both games allow up to four characters to battle on-screen at once, but Jump Superstars uses the DS' bottom screen for several unique gameplay elements: by touching a certain manga piece, you can switch characters, summon help, or even do some combo attacks. It's a pretty neat and different way to switch characters, especially when to compared to other fighting games, and is an overall nice way to utilize the DS' touch screen.
Sound-wise, Jump Superstars has some catchy music. Each area has, as expected, a different tune and nearly all of them are just great to listen to. The improvement in the amount of space DS cards have over Game Boy Advance cartridges helps the music in the sense that it sounds clearer and better overall compared to past handheld games, although it'd obviously be better if the game were created on a CD/DVD.
Jump Superstars should provide most people with a solid amount of replay value. The main mode in the game is called "J Adventure." Basically, in "J Adventure" you go through these missions spanned across four different "islands." Each "island" has plenty of missions for you to finish, and each mission has several goals for you to complete; for example, one goal may require you to break more barrels than your opponent while another may require you to not get K.O.ed. As you could imagine, the former would be easier to accomplish over the latter.
Overall, Jump Superstars is the type of game that is perfect for the DS. In addition to providing a genuinely fun experience, it also showcases the DS' second screen in a pretty unique and interesting way. It's almost guaranteed that due to all of the licenses involved in the game, Jump Superstars likely won't see the light of day outside of Japan. Still, that shouldn't stop you from checking out a FAQ at a site like GameFAQs -- if you don't know any Japanese -- and importing this game because it'd be a damn shame to miss one of the best games that the DS has to currently offer.