OK, to counter what everyone is saying, I'll play devil's advocate, the answer is usually, "no."
You can't submit a game into the Civfanatic's Hall of Fame if you do re-load, and obviously reloading isn't applicable to multi-player. But in every other situation it's an acceptable option, you just have to ask yourself whether or not it is the option you wish to select, and there's no correct answer to this; don't let anyone else influence this decision through guilt using terminology like, "save-scumming" or through fallible logic like, "if you have to ask whether or not it's cheating, it probably is." It's your game, you paid for it; play it whatever way you enjoy it the most because that's what you bought it for. Evaluate what could change and decide which version of events you'd like to experience. In single player mode, you basically have a time machine so decide if you want to go back and flap those butterfly wings.
There are some situations where I'd agree it's ill-advised, such as:
1.) you're trying to beat a personal best, earliest space-race win for example, and miss it by a turn or two, so you go back and min-max the heck out of it. Hard to argue that this is cheating yourself. While you didn't accomplish that particular goal, you still got a victory that was one of your personal bests, and you should enjoy trying that challenge again, hopefully succeeding by applying what you've learned.
2.) MUCH, MUCH, MUCH more importantly, I'd advise against reloading because you want to correct a "mistake" that put you in a situation you are unfamiliar with and don't know how to handle. If anything, I'd advise saving the game AFTER making that mistake so that you can experiment with different options in the newly discovered situation. The game will have so much more depth to you after you've discovered how to play after: 1.)losing a great city location. 2.)losing the pantheon that you wanted. 3.)missing out in founding a religion. 4.)playing after losing a city (and then winning.) 5.)Playing after losing your capital (and winning.)
There are also some situations where I'd consider it highly advisable to reload, most of which are due to being forced to make a completely blind guess, "door #1 or door#2?" when you don't have enough information at the time the decision has to be made. For example, you play as Spain, decide to explore north because it's a coin flip, and later find that had you decided to explore south instead, you would have found Uluru and GBR, both of which now have cities by them. In this case, I'd consider it cheating yourself out of a really fun game by not reloading.
oh so im screwed because you have 10 berserker at my door on turn 100 ? Let me try a different approach.
