At first glance, and based on the demographics already watching the popular animated show in the 4Kids Saturday morning cartoon block, you'd be under the assumption that Rare's Viva Piñata is a game aimed squarely at kids. That assumption would be mostly false. Because, while Viva Piñata is a game that kids will probably enjoy it is adults that will find the most fun here.
Viva Piñata is a sort of god sim where you cultivate a spot of land (a garden in this case) with plants, water, trees and various habitations in hopes of attracting a myriad of Piñata style animals. But the real interesting part of the game is its whole "survival of the fittest" food chain game mechanics that make the game really about choosing. That's mainly due to the fact that, to attract many new Piñatas, you may have to sacrifice some lesser ones. This play mechanic changes the way players may approach the game, make some species fodder for other species - even to that point of creating a sort of slave trade where certain animals are created simply for food or to sell. At the end of the day it's all about value.
Sure, you can ignore the economics of the game and simply collect your favorite piñatas, nurturing them and evolving them into their different forms, but there will come a time when you are tempted by the lure of the game's monetary system. When you get to the point where you can sell piñatas chances are you won't have a problem doing just that for a few thousand chocolate coins.
And let's face it, greed is ultimately good.
So while Viva Piñata is about raising and caring for animals there are lots of different ways to play the game. No matter your play style you favor, you'll have to expand dabbler in a little bit of these play mechanics. And there are plenty of other roles to play as well - farmer, protector, breeder, provider, collector, designer, babysitter, etc.
There are plenty of other things that you can do to amuse yourself in Viva Piñata like buying a myriad of extras from the humanoid characters in the game. If you want to put a hat on that silly snake you've got, then you can do so with glee if you have the chocolate coins. You can also purchase a variety of fruits, vegetables, and seeds that will let you grow trees, berry bushes, and produce of all kinds. Besides giving you the ability to attract more types of piñatas, these items also allow you to alter your piñata. All piñata have the ability to evolve to a certain degree beyond their original state and most of these changes are caused by food items. There are rare exceptions, but most are changed by feeding them a certain type of fruit, vegetable or seed. This evolution makes your piñata worth more chocolate coins, so it's worth tinkering with just to make some extra cash or unlock an achievement.
There is also some light role-playing in Viva Piñata that revolves around growing things. As you successfully plant, nurture and harvest things in your garden, you are rewarded with upgrades to your gardening tools and unlocking achievements. These new tools allow you to do different things and also introduce you to new piñata types and new humanoids that will provide a variety of goods and services that will further expand your game.