There have been over 3300 cricketers who've played Test and One Day cricket. The youngest player was 14 years old Hasan Raza from Pakistan who played 5 ODIs and 2 Test matches at that age. The oldest player was 52 years old W Rhodes from England, who played 8 Test matches at that age. But they are not the ones who've played the game for the longest time. Sachin Tendulkar has.
Sachin started international cricket early and is still playing the game as a 38 year old (not many 38 year olds find a spot in international cricket these days). He has played a lot of Test and One Day cricket matches all these years, and has performed well consistently. As a result, he has broken all batting records in cricket. It is unlikely that any other cricketer will break Tendulkar's batting records anytime soon.
Sachin's international cricket career spans 21 years and counting. What an athlete!
1) Tendulkar entered the game at the youngest age (debut at 16). Very few cricketers start their international career at that age. He is the 3rd youngest to play the game.
2) Tendulkar is now 38 years old and still strong. I wish he plays the game for at least another couple of years. The only other cricketers who comes close to his tenure are Javed Miandad from Pakistan (tenure 21 year, debut at 17 and retired at 38) and Sanath Jayasuriya (tenure 20 year, debut at 20 and retired at 40).
3) Tendulkar is now 38 years old and like his peers, he has reduced the number of games he plays. But unlike his peers he's still going strong. His peers seem to be headed towards retirement (see how Ponting's performance is dropping in Test and One day cricket - Runs scored and Scoring rate).
Tendulkar is exceptional. He beats the rules (normal distribution for statisticians) and sits at the edge of all distributions - debut age, tenure and performance. When he decides to retire, he will be on the edge of retirement age distribution curve as well.