Honestly, I don't think reviews have ever been as influential as developers make them out to be. The fact that good reviews correlate with good sales doesn't mean good reviews cause good sales. I think it's more likely that consumers can spy a good game on their own through screenshots, FAQs, trailers, and (most importantly) speaking with gamers and salespeople.
Regardless of how influential reviews are now, I think they're starting to lose influence to the power of trailers.
Most movie-goers don't read reviews. They attract viewers almost entirely through trailers and word-of-mouth. Only now are video game commercials on TV becoming normal. As the airwaves become increasingly saturated by trailers, I think game trailers will become more important. Afterall, most viewing of game trailers now occurs among hardcore and veteran gamers, the only people who frequent gaming news sites and official game sites. When trailers are placed on TV and in movie theaters, then they're truly reaching a mass audience and mainstream gamers.
Undoubtedly, reviews make more sense for games than films. A review for a linear story can't offer much objective information without giving the plot away. Something like Spore or Command & Conquer, on the other hand, can explain exactly how gameplay occurs without ruining the game. But just because reviews are a good resource for gamers doesn't mean gamers will be any more likely to seek reviews than movie-goers are.
Anyway, expect to see more emphasis on trailers from marketing departments in the next 5-10 years.