Retail expansion packs are a viable means for developers and publishers to increase the longevity and improve the core qualities of their best game designs. The best of these take a great game and make it even better by introducing design elements that thoroughly improve upon the original game. Many great games receive expansion packs, but the following five are the ones that stood out this year.

The official expansion pack to the popular and great strategy game Age of Empires II beautifully executes a classic formula for real-time strategy that extends the life of the original game by adding five new playable civilizations - the Aztecs, the Huns, the Koreans, the Mayans, and the Spanish - and by implementing gameplay features that let you focus more on combat than on micromanagement, all in a revamped interface.

The Ruins of Kunark is the first official expansion to the hugely popular 3D fantasy-themed massively multiplayer online role-playing game EverQuest. Not only does The Ruins of Kunark introduce a large, new continent with updated content, enhanced graphics, and challenging zones to explore, but it also features an entirely new race of lizardmen, the Iksar, which adds even more to the rich, complex fantasy world of Norrath.

A full year after the release of its hit multiplayer-focussed shooter Quake III Arena, id Software delivered this intense expansion pack that emphasizes its four cooperative gameplay modes. Quake III: Team Arena includes more than a dozen high-quality maps - including several maps much larger than any in the original game - and it adds several new weapons and tactical power-ups.

RollerCoaster Tycoon: Loopy Landscapes is the second expansion to the best-selling RollerCoaster Tycoon, and it's complex yet fun and addictive. It's a game that a wide range of players can play and thoroughly enjoy. Thanks to new decorative themes and landscapes, new scenarios, and most importantly, all-new rides that include inverted coasters, suspended coasters, water coasters, hyper coasters, raft rides, and more, Loopy Landscapes takes the original game even further.

This official expansion to the extremely popular strategy game The Sims retains the quirky humor of the original game while adding a bundle of new content, new furnishings, and a few new options that make your sims' lives even more exciting and the game more enjoyable to play.