First off, let me say, I have been a Civ Fan for many years and have enjoyed this game since it's launch. I have all the XBox Achievements and have won all four victory conditions on Deity, with Every Civ, except the Mongols.
Let the ranting begin...
Mongols
Begin the game with +50% Gold from captured cities.
Ancient Barbarian Villagers Join Us
Medieval +1 Cavalry Movement
Industrial +4 Hammers from Mountainous Regions
Modern Free Communism Tech
Starting Bonus
The Mongols start off with quite possibly the worst bonus in the game. It's nice to know that when you do conquer a city, you will be getting +50% more gold than you would have, but their other handicaps leave you so far away from capturing a city, you might as well not have a pre-game bonus.
This bonus may become useful someday, but is worthless as a starting bonus.
Ancient Era
The Second Bonus the mongols recieve allows for all conquered barbarian villages to become cities of your empire. This, at first glance, appears to give them a huge boost. We all know how many barbarian villages are out there, so it would appear that the Mongolians do not need settlers or code of laws to get an early jump on expanding their empire...
WRONG. This is by far the worst bonus in the game and is so bad, I am tempted to never achieve a Diety win with the Mongols out of spite! Here is why;
1.) Conquered Barb Villages become your city with a population of 1. Assuming you have a two food square within the 8, it will take 5 turns of growth before you can even build anything.
2.) With any other Civ, when you destroy a Barb Village, there is a Resource that pops in it's place. With the Mongols, you're city center is located on the Resource, which means it is lost forever.
3.) Barbarians Villages are randomly located by the computer at the start of the game.
Only 1 in 5 of these Villages (At Best) makes for a decent city location. It is not uncommon to have a Barb Village located in a spot with zero hammers and minimal food.
4.) If you do build a settler as the Mongols and have him build a city right next to a barbarian village, destroying the barbarian village still produces a city right next to your city.
So far, we are in the Ancient Era and have been blindfolded with our hands tied behind our backs, about to be bent over...
Medieval Era
+1 Horse Movement. WOW, now theres a bonus!! Now, assuming you've made it this far, your horses can move three squares instead of two. Ensuring that they are more susceptable to counter attack because they move that much faster than your defensive units.
Another waste of a bonus, though not entirely useless...
Industrial Era
In game, the Bonus reads +4 Hammer to Mountaineous Regions.
On the Civ Site it reads +2 Food to Mountaineous Regions.
I believe the former is correct. This is a big bonus. With an Iron Mine the Mongols get 9 Hammers from each Mountain square. Plus a Factory and Communism, that's 27 hammers per mountain square. Take into account that a new city in the modern era starts with a Population of 5, if you haven't gotten too frustrated with Ghengis' B.S. by now, you could plop down a new city deep in the mountains that could be a production power house. Not to mention the bonus still applies to the rest of your cities that have mountaineous terrain as well...
By far the Mongols best bonus, certainly rivals some other Civ's bonuses as well. Unfortunately it comes so late in the game you have probably either given up or lost by the time it gets there...
Modern Era
Free Communism Tech. I would assume that if you have gotten this far in the game, you are taking advantage of the Mountaineous Regions, have gotten or will soon get the Industrialization Tech for Factories. It would appear logical to switch to Communism the moment you get it to synergize with the Industrial Era Bonus. At this point in the game, I would imagine that you will be behind in the Victory Races and will need to break out the Can of Whoop A$$ to catch back up.
In closing, I would like to say that I hate to completely write off a Civ. Everyone has strengths and weaknesses. Learning to play a different style that takes advantage of each Civ's traits is a big part of what keeps me coming back for more. However, the Mongols feel broken to me. Their early game handicaps disguised as bonuses set you so far behind the eight ball, you might as well just play as the Barbarians.
Overall Ranking: 16th (Out of 16 Civs, Last place.)
Out of 10: 0
I would rather play Call of Duty than CivRev with the Mongols.
Let the ranting begin...

Mongols
Begin the game with +50% Gold from captured cities.
Ancient Barbarian Villagers Join Us
Medieval +1 Cavalry Movement
Industrial +4 Hammers from Mountainous Regions
Modern Free Communism Tech
Starting Bonus

The Mongols start off with quite possibly the worst bonus in the game. It's nice to know that when you do conquer a city, you will be getting +50% more gold than you would have, but their other handicaps leave you so far away from capturing a city, you might as well not have a pre-game bonus.
This bonus may become useful someday, but is worthless as a starting bonus.
Ancient Era

The Second Bonus the mongols recieve allows for all conquered barbarian villages to become cities of your empire. This, at first glance, appears to give them a huge boost. We all know how many barbarian villages are out there, so it would appear that the Mongolians do not need settlers or code of laws to get an early jump on expanding their empire...
WRONG. This is by far the worst bonus in the game and is so bad, I am tempted to never achieve a Diety win with the Mongols out of spite! Here is why;
1.) Conquered Barb Villages become your city with a population of 1. Assuming you have a two food square within the 8, it will take 5 turns of growth before you can even build anything.
2.) With any other Civ, when you destroy a Barb Village, there is a Resource that pops in it's place. With the Mongols, you're city center is located on the Resource, which means it is lost forever.
3.) Barbarians Villages are randomly located by the computer at the start of the game.
Only 1 in 5 of these Villages (At Best) makes for a decent city location. It is not uncommon to have a Barb Village located in a spot with zero hammers and minimal food.
4.) If you do build a settler as the Mongols and have him build a city right next to a barbarian village, destroying the barbarian village still produces a city right next to your city.
So far, we are in the Ancient Era and have been blindfolded with our hands tied behind our backs, about to be bent over...
Medieval Era

+1 Horse Movement. WOW, now theres a bonus!! Now, assuming you've made it this far, your horses can move three squares instead of two. Ensuring that they are more susceptable to counter attack because they move that much faster than your defensive units.
Another waste of a bonus, though not entirely useless...
Industrial Era

In game, the Bonus reads +4 Hammer to Mountaineous Regions.
On the Civ Site it reads +2 Food to Mountaineous Regions.
I believe the former is correct. This is a big bonus. With an Iron Mine the Mongols get 9 Hammers from each Mountain square. Plus a Factory and Communism, that's 27 hammers per mountain square. Take into account that a new city in the modern era starts with a Population of 5, if you haven't gotten too frustrated with Ghengis' B.S. by now, you could plop down a new city deep in the mountains that could be a production power house. Not to mention the bonus still applies to the rest of your cities that have mountaineous terrain as well...
By far the Mongols best bonus, certainly rivals some other Civ's bonuses as well. Unfortunately it comes so late in the game you have probably either given up or lost by the time it gets there...
Modern Era

Free Communism Tech. I would assume that if you have gotten this far in the game, you are taking advantage of the Mountaineous Regions, have gotten or will soon get the Industrialization Tech for Factories. It would appear logical to switch to Communism the moment you get it to synergize with the Industrial Era Bonus. At this point in the game, I would imagine that you will be behind in the Victory Races and will need to break out the Can of Whoop A$$ to catch back up.
In closing, I would like to say that I hate to completely write off a Civ. Everyone has strengths and weaknesses. Learning to play a different style that takes advantage of each Civ's traits is a big part of what keeps me coming back for more. However, the Mongols feel broken to me. Their early game handicaps disguised as bonuses set you so far behind the eight ball, you might as well just play as the Barbarians.
Overall Ranking: 16th (Out of 16 Civs, Last place.)
Out of 10: 0
I would rather play Call of Duty than CivRev with the Mongols.