I know it's early to jump the gun, but the more I see, the more convinced I am that Mass Effect will be the best game released this year.  Truthfully, I don't think anything else will even be that much of a threat.  Ratchet, Uncharted, Mario Galaxy, Metroid, Halo 3, Bioshock... all great games.  But Mass Effect is looking like the kind of game that can change the entire landscape of the industry.  It looks like the game we have all been waiting for since the "next-generation" even arrived.  In short, it looks like the game that can reshape expectations on what a video game can actually be.  I am not saying this as a die-hard Bioware fan.  I didn't like KOTOR that much; I thought it had some great ideas, but it was hampered by it's poor graphics and clunky battle system.  Jade Empire had an even worse fighting engine (though better graphics) and an overall execution that was nowhere near as ambitious as KOTOR.  
But Mass Effect looks just incredible.  It could change everything we know about video games, like the way Mario 64, Resident Evil, and Tomb Raider did back in 1996.  Or the way GTA, Metal Gear, and Halo did in 2001.  I have been wrong before.  But at the very least, I expect Mass Effect to garner GOTY.