Watching 
Will Wright's presentation on Spore (worth registering, and worth the hour), I'm inspired by his dazzling display of old meets new.  It's a pile of tried and true idiomatic gaming mechanisms - the pacman bit, the diabolo bit, the populus bit, the sim city bit, the civilisation bit, etc. - but fittingly it's more than the sum of its parts.  The ultimate po-mo mish-mash, shamelessly derivative in terms of taking the known good bits from many sources; ripping, mixing and burning and creating something exciting and new.  If it's as good as it looks - and I hope it is - then bottom-up game world building is here to stay.  I haven't bought a PC game for about 8 years, but Will Wright has me sold on this one.