I've never played Civ4 before, but I have Spore and it is amusing. You can never actually "beat" the game. But once you get to the Galaxy level the gameplay drops off. They now have an expansion pack which should make the game way more fun.
spore's more interactive and childish while civilization is more detailed and strategy. I would go with civi.4 because of the 3 expansion packs and the fact that there really isn't any strategy in tribal or civilization stages in spore. plus when u get bored with normal gameplay you can play scenarios in civ. 4 like WW2 and space ships
