The major similarity between these two revolutions is that they were both waged against an unpopular autocracy.  The Russian Revolution was meant to overthrow the monarchy while the Mexican Revolution was intended to overthrow the autocratic rule of Porfirio Diaz.  It is also worth noting that both revolutions were followed by civil wars between various factions that wanted to take power.

The major difference is that the Mexican Revolution was largely a revolution in favor of democracy.  The Mexican Revolution did not lead to any sort of a communist government.  The PRI was not perfectly democratic, but neither was it totalitarian in the way that the Soviet government became.  

These two revolutions were fought to overthrow unpopular autocratic governments.  But they had very different results in terms of the governments that they put in place to replace the autocracies.

Compare and contrast the Russian and French revolutions.

Despite the French Revolution occurring over a century before the Russian one, in many ways it took place in a far more advanced political and economic system. While Russia in the late nineteenth century consisted of a small nobility and large population of serfs, with only a small middle class, and a limited agricultural economy, France had a substantial class of educated bourgeois and a far more diverse economy and better educational and administrative system.

The French revolution was essentially a capitalist and democratic one, while the Russian one was communistic and authoritarian. The French, after a relatively brief period of instability, had the necessary educational and economic base to transform their nation into a successful modern state, a condition that continues to elude Russia.