All RPG (Role-Playing Games) developed for the PC (Windows) platform.
Due to the massive size of RPG titles available for the PC, I've broken them up into four distinct categories; Epic RPG, Action RPG, DOS Classic, and Massive Multiplayer Online RPG (MMORPG). Though some hybrid titles and recent FPS-style RPGs really blur up these RPG genres, the best way to distinguish them is this way:
Epic RPG: Massive worlds, long gameplay (50+ hrs is typical), very detailed levelling up & characters stats, more open-ended gameplay, slower-paced but detailed quests. (Oblivion, Baldur's Gate)
Action RPG: Hack'n'slash gameplay, more linear storyline, usually automated levelling up and less dialog with NPC characters, which gives it more action feel to the game. (Diablo, Dungeon Siege)
DOS Classic RPG: Cut-off is around 1997/98, with the launch of Diable and Baldur's Gate. Any DOS-based games before that, wether they were epic or action RPGs, will go in this category. (early Ultima series, D&D Gold Box games)
MMORPG: Any RPG played online in a massive universe populated by peer gamers. (World of Warcraft, EverQuest)
This list is sorted by Listal popularity, but unreleased titles are at the end of the list until launch date.
I think I've got most of them, but if missed one, please let me know via comments below.