Well, I see three major innovations in Spore, that I haven't even heard of in games before now. The first is that "powers of ten" concept with the huge range in scale. The second is the huge emphasis on player-created content created. And thirdly choosing what content to provide the player based on how he/she is playing the game.
If we see a ripoff of Spore it would most likely mimic the range in scale, since I see that as the most obvious "amazing" thing about Spore.
I could see some kind of SporeWar game where you begin as a lone soldier (Wolfenstein), then gain command of a small band of heroes(Rainbow Six, maybe X-Com), and eventually work your way up to command of larger groups(Starcraft-ish), entire armies(historical war games), nations(Risk?, Civ?), and perhaps even unto planets at war. A few games have done a little of this, like Giant: Citizen Kabuto, but seemed to use it as a gimmick instead of focusing gameplay on it, but once (if?) Spore sells like hotcakes designers and publishers would probably be more receptive to this kind of idea.
If I was to make a prediction, I might take SimCity/SimCopter as an example and say that you will see action games that utilize the content made in Spore. Accessing the huge DB of unique (and free for EA) content for an endless world of cities and monsters for an action game might be cool. Spore of the Rings? Need for Spore? The Sims: Alien Planet???
scary. that last one.
