A lot of my brain time has been preoccupied lately with thoughts of accessibility in games.  Obviously games have a lot to offer as a medium, but there are some elephants in the room when it comes to introducing new or casual gamers to games that are thoughtful and carefully constructed.  I think one of these elephants might be Gravity.

Anecdotally, these are some games that have been very popular with non-hardcore gamers that I've known over the years:

Legend of Zelda (various iterations)

Mario Kart

Doctor Mario

Secret of Mana

Super Mario Bros. 3 (and, to a lesser extent, Super Mario World)

Katamari Damacy

Flower

Sim City

Mario Party/Shitty TV Trivia/Whatevers

World of Warcraft

Pikmin

Wii Sports

Obviously there are a lot of reasons why these games are all very popular across some pretty broad demographics.  I think a major contributor is that Gravity, and its bitch of a sister Jumping Puzzles, are largely absent (with the lone exception of Super Mario - would be curious to know exactly what percentage of SMB3 levels in particular are dependent on genuine precision leaps).

The title "Gravity Porn" is a reference to games like Prince of Persia (the original, or "classic" version) which rely on realistic interpretations of Gravity and are thusly completely F'ing brutal.  I love 'em still, but as a designer I am starting to see that sort of thing as a major impediment. 

Of course, I'm not the only one!  They didn't add the ability to rewind time to the modern iterations of the series for nothing...