I'm just going to throw a few ideas in here.
High Barriers to Entry: This is a major one. If you want to see a new movie, you just spend $12 or so for ninety minutes of entertainment. If you want to play a new video game, you have to spend $60 or more. Before you can play it, you need a $300 machine and a TV that can interpret the A/V signals, generally $100+. Granted, the system and TV are one-time expenditures, but you can see the huge difference in initial entry.
Risk Aversion: Modern games cost about $30 million to produce. The publisher fronts the money in exchange for a product at the end of the development cycle (generally two years). If that game doesn't sell a certain number of copies (it goes through so many markups before the final $60 that the developer is lucky to see $3 from each sale), then the publisher loses money and the suits are less likely to approve another $30+ million for a similar title. They do all sorts of market research to see what's hot, and more importantly, what's a guaranteed return on investment. Publishers don't care about cool games, they care about making more money than they invested in the development and distribution.
Lack of Mainstream Recognition: A hundred years ago, the moving picture was a strange new technology encroaching on theatre's niche. In the last fifty years, video games have become an entertainment juggernaut, outpacing film's money numbers year after year. Still, the mainstream media marginalizes video games, still seeing them as the toys Nintendo marketed in 1986. Nothing we have done has changed that, and in some cases makes our medium look reactionary and childish.
A Preponderance of Brown and Grey: Game engines can't do radiosity very well, and the level designers aren't much better, it seems. The human eye can tell when light isn't absorbing a colour when it reflects (that's radiosity in a nutshell). The devs fall back to grey and brown, which don't reflect much coloured light, since this is easier than tuning every illuminated surface in the game. This shortcut means new games can't achieve their own visual identity.