For some reason, every time I go browsing through the Blu-ray section of a video store, I almost invariably hear somebody condescendingly explain to their wife / girlfriend / mistress / whatever that Blu-rays are for special effects, and should not be wasted on dramas or comedies. This attitude perplexes me. If anything, special effects don't look that great in high definition, because the increased resolution is more revealing of the methods of their creation, whether optical or digital. Dramas, on the other hand, rely on acting, and the more nuanced the performance, the more involving it is in high def. Francis Ford Coppola draws attention to how much more effective Al Pacino's performance is in the Louis' scene in The Godfather, where the actor is playing a character who is himself acting a role. The layers are barely visible in standard definition, but become much more apparent in high def.²
Another area where high def tends to excel is in filling in detail in the characters' environment. Due to the nature of the compression required to fit a movie onto DVD, the bandwidth tends to be devoted more towards preserving faces and movement, which means that on a larger screen the compression artifacts and pixelation are more apparent in the background. How important this is to the viewing experience depends greatly on the nature of the film, of course, but a movie like Amadeus, with its lush sets and elaborate costumes, is a demonstration of exactly how that can be a benefit.
This is a similar issue that I have mentioned before with respect to the tendency among home theater enthusiasts to demonstrate a good sound system by playing the loudest parts of the movie. Yes, that can and should be impressive, but what often makes an effective sound mix is how it handles the quieter portions of the film, the balance between the dialogue, diegetic sound and music, the way that the sonics reflect the physical space being displayed on screen. With a few exceptions — Master and Commander: The Far Side of the World being one of the most notable — the loud portions of a film often have a very similar quality to them; this isn't a criticism, it is simply the nature of the beast.
I found this amusing tidbit on Fark.
¹ — Okay, maybe the "lean" part is a bit of a stretch... insert "stretch mark" joke here.
² — I have mentioned before that seeing The Godfather on the big screen allowed Robert Duvall's performance in his scene with Al Lettieri to be much more impressive as well with subtle qualities restored to the Blu-ray edition but barely visible in standard def, if at all.