When it comes to brothers, it's always easy to point out the differences. In the case of Oasis, Liam Gallagher's the grumpy one who mainly sings, while Noel is the slightly less grumpy one who writes the songs and doesn't mainly sing. Gary Neville is the Man Utd player who dislikes scousers, while ex-Man Utd team mate brother Phil now plays for Everton. Even in the realm of computer games, portly red-clothed plumber Mario is a world famous icon, while skinny green-clad Luigi is a world class nobody.

Together, however, brothers have power. Oasis became the biggest band of the 1990s, the Nevilles helped United to their 1999 treble, and when it comes to trouble in the Mushroom Kingdom, Mario and Luigi have been saving the day for decades.

But in Mario & Luigi: Partners in Time, one set of brothers just ain't enough.

As ever, the problem is complex. Nutty scientist Professor E Gadd has invented a time machine and Princess Peach has vanished, presumed kidnapped by the Shroobs, an creepy alien race who've turned up in search of a new home. Travelling back in time to clear up the mess, Mario and Luigi come across baby versions of themselves. In terms of creating a setting for a great game, it's a quadrophonic match made in Mushroom heaven.

For most of the game, the little fellas sit happily piggyback on the shoulders of their grown up selves, adding extra firepower in battle. Each character has special abilities too, which you'll need to make your way through the game. Most obvious is the way baby Mario and Luigi can be thrown into the air to reach high up areas or tall pipes. They can also be squashed flat to slide under doors and each has a hammer – useful for bashing things. These baby-only missions are some of the hardest of the game though, as the babies are weak and the powerful four-way attacks aren't available.

For like many role playing games, the trick in Partners in Time is knowing when to pick your fights. It's relatively easy to start a scrap – they're triggered when your characters walk into an enemy. Alternatively, if you're feeling confident you can get your attack in early by bouncing on an enemy's head. Either way, once a bout is started, you'll switch from the main screen to a special battle mode, where each side takes it in turns to make their moves.

And it's here that Partners in Time demonstrates its brilliance. You start out with simple attacks; in typical Mario-style, you can jump onto your enemy's head, pressing the action button at just the right time to cause maximum hit points. When combined with either baby Mario (or baby Luigi for Luigi), however, you press their button first, before getting an extra attack as the heavier, old version somersaults back into the air. Even more exciting is the ability to counter-attack. As before, it's a case of pressing the correct character's button (each brother is permanently assigned 'A', 'B', 'X' or 'Y') as an enemy makes their attack. Sometimes you'll dodge their attack. Other times you can reflect it right back.

This layering of the brothers' abilities – pressing the right button at the right time, plus special items such as fireballs and kickable eggs – creates an enormously satisfying and flexible selection of attacks.

Of course, this might all sound much too complex to be fun, but thanks to the combination of the game's audio and the beautiful character movement, you quickly get into the rhythm of what to do, and when. Compared to hardcore role playing games, the learning curve is just right too. Each level has a save point, so you'll rarely have to repeat bits of the game, and even the bosses, once you've learnt their attack patterns, are fun to beat.

But as well as combat, Partners in Time has plenty of other charms. The graphics, despite being two dimensional, are fantastic and the animation, whether it's the complex attacks of Mario and co, or the comic worry of Peach's faithful stewart Toadsworth, is always spot on. And it's a similar story in terms of the game's humour. Luigi is the butt of many falling-down jokes, while other characters, from the cookie-chomping greed of baby Bowser to the twisted Japanglish of helper Stuffwell are beautifully pitched.

In fact, we think this is as close to perfection as a game can be. It's huge (a good 30 hours long), always fun to play, full of brilliant fun, and always keeps you excited and wanting more with well-designed levels – there's one where you play through the innards of a giant pink dinosaur that is particularly great – new items to play with and new tricks to learn. Oh brother, what more could you ask for?

Mario & Luigi: Partners in Time is on sale now.