Skill level will always be the "first factor." A player of superior skills and a bad map should still defeat an inferior player w/ a good map a majority of the time.
Players with a host of games under their belts have seen so many bad maps, they have learned how to cope with them, and make the most out of poor starts, lion packs, hill berries, desert wastelands, backyard enemies, etc.
Back on the original point, if indeed there was one, is that, no, indeed, the civs are NOT balanced, nor were they ever intended to be. If I square off in a 1v1 against Hemlock, a player of similar skill level and experience, chances are it would come down to civs (and our familiarity w/ them).
So, for instance, if we chose Random Civs, and I got Carthage to Hemlock's Assyrian, with the maps being roughly equal, Hemlock should be the victor - a "fast" civ with a strong Bronze should defeat a "slow" civ with a comparably weak Bronze.
Um, it was Winner buys the beer, right? And no, Hemmie, I don't drink ROOT beer.