The question of who should be able to vote is interesting. The Declaration of Independence contains the concept that governments "[derive] their just powers from the consent of the governed." There are people who have lived their entire life in the country who don't have a voice in government.
Currently you must be a United States citizen (Who can vote). I'm not sure this is reasonable.
Here are a list of what I consider reasonable requirements:
Reside at a particular address in the United States for at least the last 6 months
Be at least 18 years of age
Have a reasonably secure form of identification (e.g., drivers license)
Have passed the citizenship test within the past 10 years (Citizenship Test Questions)