Only three or four games have
wowed me--especially after playing them. Shadowrun first edition was
wow-inspiring to look at, but
groan- & cringe-inducing to play. Noumenon is a really, really
WoW! game idea. But it requires complete buy-in by everyone, or it doesn't work; I've wanted to use the game as an ontological experiment in a philosophy class, but ... Alas! Never got tenured while teaching, so I never had the chance.
Delta Green's ingenuity of making a band of investigators in Call of Cthulhu work. Chaosium could have done this years before Delta Green with their Theron Marks Society insert booklet, but they never did anything more with the idea than than one-off-and-forget-about-it booklet. Delta Green grew into a great investigative game that compels the characters to make pragmatic decisions amidst the Weird and Unnatural circumstances. Not many rpgs force the consideration of what to do with the body of who or what the characters have just killed. Or, afterwards, to confront their mundane life of family, friends, and day job.
I haven't verifiably encountered Cthulvian beasties, but I'd guess doing so, especially more than once, would change how I dealt with the husband and the job and the folks stocking shelves at the grocery store.
Nephilim really, really wowed me. Both the original French game and the English translation. Still ranks with me as perhaps the most impressive rpg character building I've ever encountered. The breadth of scope this game has is breathtaking. And the game has some of the most grounded perspective of real-world occultism any rpg has offered.
I certainly cannot definitively state I have lived a dozen lives as the same preternatural sapient being, but I imagine I would remember lucid snippets and retain elements of them while inhabiting this proverbial meat covered skeleton composed of stardust as it rides on a rock hurtling through space.
But of all wow-inducing games, first edition Twilight: 2000 is, by far, the most impressive rpg I've heard of, read, or played. Sure, the military orders of battle details are astounding, but more impressive is to have been able to capture the authenticity of human survival of an almost-resourceless setting in dice mechanics; it is a staggering accomplishment. Granted, implementing such is up to the gm and players involved (I've seen more
handwavium fantasy in post-apocalyptic games than probably any other genre--thanks, Hollywood), but the mechanics of the reality is written into the game. Equally as impressive is the tapestry of moral crossroads provided to allow (like human freewill itself) for characters to behave indecently, if that's the vile road they wish to take. Both surviving and having to make a conscious choice to behave either deplorably or with ethical morality are the dilemmas humans face in such a situation as
the world around you is fuct, so what do you do now?
Unlike the previous two examples, I
have survived a post-apocalyptic military siege for four years with almost no resources and being forced to make decisions that should only ever have to be made in a fictional or philosophic setting.
Perhaps if I hadn't survived, I wouldn't care for a game that mimicked such a situation. But I did, so I very much do.