Pokémon is a consistently popular franchise, and a real money-spinner for Nintendo, but to date the mainline games in the series have been confined to handhelds.
Sure, there have been console-based spinoffs such as the vastly underrated Pokémon Snap and numerous others, but Pokémon is still primarily a "Nintendo handheld" franchise.
While Nintendo handhelds typically have a huge install base to supply new Pokémon games to, it's somewhat baffling why Nintendo and developer Game Freak have remained resistant to a number of things that fans seem to be hungry for -- specifically, a true console-based Pokémon game, and a massively-multiplayer online version of Pokémon.
Speaking with VG24/7 recently, Game Freak director Junichi Masuda noted that X and Y's player search system on the bottom screen made it eminently suitable to handheld play, both out and about and in the home, and that "if the Wii U were to be portable in its own right, we'd probably reconsider" the question of bringing a mainline Pokémon game to consoles. It's unfortunate, as a Wii U-based, HD, 3D, online Pokémon would probably help out Nintendo's struggling console a great deal, but it's unlikely we'll ever see it -- much as it's unlikely we'll ever see a smartphone version, either, due to Masuda's insistence on the game being played in a "safe" and "fun" environment free from the DLC and microtransactions so beloved of mobile platforms.
And yet despite Game Freak's resistance to the idea of making a "console-style" game in the Pokémon franchise, there's clearly demand for it. So much so, in fact, that one fan, known as "Xatoku," has set about making his own, known as Pokémon Generations and built using the popular Unity framework.
Pokémon Generations professes to be a "free action/adventure/RPG inspired by both the Pokémon anime and the Pokémon video games." The game is set to include both single- and multiplayer content, and feature a story that bridges the gap between the first-generation (Red, Blue, Yellow) and second-generation (Gold, Silver, Crystal) eras. The game isn't finished as yet, but active development is still taking place -- albeit at a slower rate than originally intended as Xatoku is also working on other projects that will actually make some money and lead in the direction of a career. Xatoku's eventual plan is to run a Kickstarter for a new, all-original game, then work on that full-time and continue to provide updates for Pokémon Generations as a hobby every two weeks or so.
You can find out more about Pokémon Generations here, and follow Xatoku for the latest developments on Twitter. Xatoku is keen to stress that the game is purely a hobby project and not intended to make any money directly, but also notes that he needs to pay his bills somehow, too. Until he launches a Kickstarter for his upcoming new project, you can help out costs for server hosting and other, non-Pokémon Generations-related costs, with a donation.