It seems every piece of media in the world gets rated nowadays. Magazines, websites, all sorts of things exist to get reviewed and a number slapped onto them. I'm personally a big magazine fan - I get Official PlayStation Magazine and PC Gamer UK every month, and magazines like PSM3, Xbox 360 World and Official Xbox Magazine to fill the empty half of the month where I've read the two regulars.
But the rating systems irk me a bit. A great game will get the perfect rating, then a significantly better game will be stuck to get that same rating despite being better. An instance of this - Metal Gear Solid 2: Sons of Liberty was given a 10/10, with 10 rewarded in each individual aspect too, in the old Official PlayStation 2 Magazine. This was, like, 17 issues in - the magazine ran for 100, covering the entirety of the PS2's popular lifespan. Sure, it's a very good game. But perfect? In comparison to some of the other stunning games PS2 got? No way.
Another annoying thing with current rating systems is they falter when non-significantly-different sequels to games come out. Dynasty Warriors is the perfect example - there's been, like, seven of the main games, and they differentiate so little it's almost embarrassing. But magazines, peeved by this, kept rating the sequels lower and lower. This is despite them being technically superior!
So my idea is this - a relative, uncapped rating system. There is no perfect score. It starts with 100 being as high as is expectable at the time, and 0-10 being god awful. So you could have given Metal Gear Solid 2 a 95-100, yeah. But by the time games like TimeSplitters 2 and GTA: Vice City come out, they could start nudging 105 or so. The stellar games late in the console's lifespan could be getting 150-200, with even the lesser games in the 100 region thanks to their ability to get more out of the system. Then, when the console's successor comes out, the games could continue to be compared to this system, with the likes of Metal Gear Solid 4 perhaps getting 250.
This would also be good for the repetitive sequels. Dynasty Warriors 193 could get the same score as Dynasty Warriors 192, which is fair - but all other, more original games would be constantly raising the average bar, leaving that game behind.
While it's true there's no "maximum" to aim for (and it'd mess with aggregation sites like Metacritic), the highest-rated game at the time could be the one to beat. Anyway, I just feel this would be a superior way of handling ratings to the current "GTA: San Andreas - 100%! GTAIV - wait, shit, 100% as well I guess!".