I have managed to stay away from this topic for quite some time now. I usually avoid religion, but I can't maintain my silence any longer. So due to lack of self- control, I shall add my few bit.
Perhaps one of the biggest criticism that Islam faces is the permission that men are allowed four marriages. It is a very critical and mindboggling idea, but I don't think its completely incomprehensible. Personally, I believe that everything in life is progressive, with time things change, and circumstance gives rise to various situations. Keeping that in mind, it is logical to assume that even this concept of polygamy is based on the older days. Why is it that we know smaller things, such as sightings of the moon with the naked eye are not necessary anymore, due to NASA's presence, but we fail to see that perhaps polygamy is no longer necessary either?
A major aspect of that is perhaps overlooked is that polygamy is permissible in Islam, neither is it compulsory, nor is it encouraged. If you go back about 1500 years ago in history, it makes sense that men were allowed to marry multiple wives. Men going off to war were more prone to dying early and creating a shortage of men. Women, working inside homes, caring for the home and kids, needed husbands back then. And therefore, since not all women could have a men to themselves, it was considered acceptable for men to have multiple wives. Coming back to today's world, women are able to lead a life without a man, they have become independent enough to work and care for their homes, and therefore, the need for polygamy has also disappeared.
Another aspect of history is that it was traditional, acceptable, and valued for men to have many wives. It was a sign of wealth and status. With the introduction of Islam and the Quran, there was actually a limit placed on the number of wives that a man could have. If you think about it, men who had hundreds of wives at that time, were now limited to only four (why four is the magical number - i do not know).
Also, in my opinion, and based on my research, the Quran clearly states that men are allowed four wives, if and only if they can maintain them equally. I personally think that there is no way that a man can maintain equality among four women, I don't think that human nature permits us to treat others equally. Therefore, I personally believe this concept to be null and void.
Another aspect of polygamy that is overlooked is something I find interesting. In Islam, a man is not allowed to marry a married woman, however, a woman is allowed to marry any man that she wishes to, as long as he has no more than four wives.
Now, we come to the golden question - why a woman isn't given the same rights. I think its simple, Islam is very concerned with the identities of the mother and the father. If a man marries multiple times, the identity of both parents is clear. If a woman marries multiple times, the identity of the father becomes of question. Due to Islam's nature of family-oriented culture, that is unacceptable. Granted now we have DNA tests that will permit us to discover the identity of the parents, this technology was not available 1500 years ago, when these concepts were first introduced.
As far as the argument that men and women are the same, well, I don't think so. Men and women are equal in beliefs and actions, but they are not the same.
On a final note, although men are permitted four marriages in Islam, research shows that most Muslim men are monogamous.