Haven't played 5, but the AI cheats enough in the earlier games that having an advantage doesn't seem like too much of a bad thing (I never did well on difficulties above Prince). Every country hating your guts and declaring war on you as much as possible (but not on each other) was always really annoying.
It's like that in 5 as well. That's a weakness of the series, I think - they can't really make smarter AI so they just penalize you more for going up in difficulty. other civs get various bonuses, you get happiness penalties, etc. it's not swell and not really balanced. I think there's a good reason to play on normal difficulty and that's enjoyable, even if it's pretty easy.