For a company so devoted to couch co-op, 3DS is an odd choice for Mario Party: Island Tour. Handheld systems are innately a singular experience, so a party game steeped in the raucous tradition of Mario Party doesn't immediately feel like a perfect fit. Despite some efforts to compensate for the new platform, its handheld nature ultimately undermines some of the series strengths.
Single-player has never been a focus for Mario Party games, and only the most passing of attempts is given to justify it here. You can play normal game modes against AI opponents, but none of them seem terribly bright, and they're laughably bad at the mini-games that give boosts. Bowser's Tower is the meatiest single-player offering, but it's simply a lengthy endurance mode.
That would be fine, except the mini-games vary wildly in quality. While they're uniformly simplistic, a handful manage to be clever. Others are outright frustrating, particularly when they try to ape the style of classic Nintendo games. While the game can often look like traditional Mario platformer, the mini-games rarely control as fluidly, making for a jarring experience.
Multiplayer should be where Mario Party shines, and to its credit, Download Play is robust. I was able to enjoy a wide variety of modes with only one copy of the game, which is an absolute must for such a casual title. Of course, that also means it requires multiple 3DS systems, so it's not the type of game that can be easily tried out with non-gamer friends and family. The lack of online play is clearly a drawback. It seems as if Nintendo abstained from online to retain its couch co-op legacy, even if 3DS isn't the best platform for it.
To the extent that Mario Party is a virtual board game, Island Tour does offer a nice variety of game types, tied together by giving rewards for competing in the mini-games. The loose conceit lets them offer some strategic choices, like banking rocket boosts in Rocket Road to act as dice roll multipliers. Others, like Banzai Bill's Mad Mountain, feel much more luck-based, since a single stray dice roll can fire a mortar that will send everyone in its path flying. It really will depend on how much randomization you want in your game. (Island Tour rates each board on attributes like Skill and Luck, but I found those ratings didn't align with my own estimation of those attributes.)
Mario Party: Island Tour never seems a natural fit on the 3DS. It feels more like the game has been hammered into shape to fit as well as it can on the platform. Yet, with no online support and inconsistent mini-game quality, those concessions just aren't enough to warrant the franchise's move to handheld.