Super Mario Galaxy is currently beating out The Legend of Zelda: Ocarina of Time by just 0.2% for the highest scored game of all time .  Ocarina has almost continuously held the number one spot for nearly a decade.  Today Galaxy has a 97.8% and Ocarina a 97.6% average score, but Galaxy's lead is narrowing because yesterday they had 97.9% and 97.5% respectively.  It's also important to note that since yesterday Ocarina has gained a review and Galaxy has lost one, and that Galaxy is currently losing in the GameRankings.com user vote. 

Other games like Halo 2 have previously beat Ocarina for a couple of days, but could not hold the title.  I have a feeling Super Mario Galaxy will survive the test of time and stay in the top two, but I might be making a similar blog post around February tenth. 

Update:


For comparison:


Source: gamerankings.com