And may I ask why you prefer Civ 4?
I've seen a few other people claiming that it's better than 5, if that's really the case I might pick that one up instead!
You may certainly ask. Don't get me wrong, Civ 5 is playable and (again) I don't want to start a fight with those who like it. But I preferred Civ 4 because almost everything that changed in Civ 5 was (IMO) for the worse. Just off the top of my head...
Religions. You actually had religions in Civ 4. Sure, the designers bent over backwards to avoid offending anyone (every religion had the same effect game-wise), but I liked how you could use/abuse them. You could spread them to your neighbors to build alliances, you could use them as tools to boost your culture, and you could make a fuckton of money off religions you controlled. Of course, the sword cuts the other way, too, and civs of OTHER religions would hate you more, but that just made life more interesting. ALL of that is gone in Civ 5. Wait, there was a piety social policy, but whatever. Speaking of which...
Civics. In Civ 4, you could switch civic options if you didn't like yours anymore. In Civ 5, you have to buy "social policies" with culture points, and there's no going back. This is somewhat counterbalanced by Civ 5's policies having no downsides (if I remember right), but I liked the Civ 4 way more.
Barbarians. In Civ 4, they were more than camping nuisances you could wail on for some pocket change. Barbarian cities would pop up if the map remained untamed long enough, but that was something else that could work in your favor, as you could conquer them and add them to your empire. (Or just raze their savage asses and leave the ruin tile on the map as a monument to your badassness.) So that's gone, too. I guess that's what Civ 5's new city-states are for...
Leaders. Civ 5 only has one leader per civilization (in Civ 4, most had at least two), so nowhere near as many choices starting out. And while we're on the subject of leaders/civs, I hate Civ 5's DLC civs. It feels like they're just trying to squeeze more money out of something that should have been included in the game to begin with, rather than making an honest expansion pack.
Diplomacy. Civ 5 diplomacy is definitely worse. Granted, in Civ 4 if you refuse to help someone, they'll still hold it against you 3000 years later. But in Civ 5 you get denounced by civs for no apparent reason, even if they liked you last turn. Oh, and instead of trading techs, you have to get a research treaty and wait 20 turns. Ugh. I can actually see why that was put into the game - it's nice that less powerful civs can help you technologically, even if (in Civ 4) they'd have no techs to offer. But I miss tech trading.
Mods. Civ 4 inspired a lot of awesome mods in its time, including Fall From Heaven, Planetfall, Dune Wars, and only about a zillion mods that overhaul the main game (Rhye's And Fall of Civilization, Rise of Mankind, Realism Invictus, etc). Rhye's and Fall From Heaven, in particular, were sufficiently great that Firaxis actually included stuff for them on Civ 4's last expansion pack. Civ 5 also has a lot of mods, but fewer projects as ambitious as those. (To be fair, that will probably change as Civ 5 gets older.)
Other Things. Civ 5 requires Steam... too bad for people like me who hate it. The ranged combat also annoys me. It makes sense for things like artillery, but I will never understand why archers are ranged while modern gunmen aren't.