No one has really mentioned "Jungle Cruise". In Birnbaum's guide they actually say it's better during the day (funny for them to be that decisive) but I find the opposite. In this day of AK, and the safari with real live animals, the good 'ol JC can seem rather antiquated. I did it several times during MNSSHP's last year and had a blast because it was like a whole new ride - things were a lot more "convincing" (or at least less fake looking) by dark.
As to the dark-rides during the day thing, yes, I have so noticed that as well. At night, when your eyes are properly adjusted, you can see things more clearly in a way, but the illusion is lessened. A great example of this is the cannon-ball scene in PotC. During the day, it's very hard to see the ceiling, but at night I have no trouble picking it out exactly and seeing the seams/etc. Same as someone mentioned above about Haunted Mansion and the screen in the graveyard - much easier to make out at night (and those spit balls and assorted imperfections are more obvious).
It's because of those reasons I actually prefer, for illusion sake, to ride those during the day. I also have to agree with Laura22 - I can't tell you exactly why, but Splash Mountain is much creepier at night. Maybe it's the whole indoor/outdoor combination, or the simulated "outdoors" inside (if you get my drift). And those crows just look so much more meanacing...
AEfx