The Non-Euclidian Staircase

I do so much multi-genre play (Feng Shui and Amber) that this is kind of tricky, but I do have a few...

Real World Historical (true or "alternative"). I'm a big Harry Turtledove and Eric Flint fan, so something like Turtledove's How Few Remain (and sequels) or Flint's 16XX books would trap me in a minute. By this, I mean something firmly in the "real world" with just enough changes to make it unique and unpredictable. This separate from the (also attractive, IMO) style with more dramatic changes, such as Godlike.

The Classical Bronze Age (Greek/Trojan/Hittite/Egyptian/Babylonian or something with a similar feel) is very appealing, which helps add to the temptation of Testament despite the d20 mechanics (which I don't find do realistic-level very well at all). This has always been the appeal of RuneQuest to me (I don't much like Glorantha), and is the reason I have my own fantasy world (mentioned here) set back at this technology level.

And Westerns. I love westerns, particularly of the gritty 60's style. Sergio Leone did the world a great favor when he borrowed Kurosawa's Yojombo to make A Fistful of Dollars. TSR's old Boot Hill was never all that good, and few other mass-market games really did the genre justice. To me, Deadlands is too populated by weirdness. But Dust Devils is quite tempting...

I guess what all of these have in common is a reduction in the element of the "fantastic" (which is all too common in RPGS) in exchange for more of the "real" (which is too often absent). Of course, "real" is very much informed by movies and books here, so still likely isn't exactly authentic.