"If players like him (Sachin Tendulkar) don't play the longer version of the game, Test cricket will die. I pray to God he continues to play Test cricket. I was very happy to know he has retried from ODIs. For me Test is education and the shorter versions are entertainment," Ranatunga said.
Ranatunga, who guided Sri Lanka to their first and only World Cup title in 1996, said Tendulkar still has a lot of cricket left in him.
Asked whether Sachin was on a comeback trail after scoring two centuries in domestic matches, Ranatunga said the Mumbaikar, despite being 39, is a much better player than some of the younger Indians.
"If Sachin Tendulkar plays one good knock, I am sure he will play two-three years more without a problem," he said.
On to issues facing international cricket and Ranatunga came down heavily on the ICC, calling the sport's world governing body "toothless".
Instead of blaming the BCCI for the non-implementation of the controversial Decision Review System to avoid umpiring mistakes, Ranatunga turned his ire on the ICC.
"I am not blaming BCCI, but blaming ICC for not making DRS compulsory. They should not allow home countries to take decisions on the matter," he said on the sidelines of Sri Lanka Tourism promotion event here.
"They (the ICC) shout, but hardly bite. I have always said that they haven't changed. ICC should protect the game not individual countries on the DRS issue," he suggested.
Ranatunga said even if the Indian Board pushes the ICC into a corner, it should have the spine to take bold decisions and make it mandatory for all nations to use DRS. "This system is the best thing that has happened to cricket in the last 20 years and I feel DRS should be adopted by all countries. We would have been better batsmen, bowlers and fielders if the DRS was there in our time," Ranatunga opined.
Ranatunga said Twenty20 has ruined cricket as it does not create technically sound players such as Sunil Gavaskar, Sachin Tendulkar, Gundappa Vishwanath, Mohammad Azharuddin or Dilip Vengsarkar.
"They are more concerned about playing the shorter version of the game, earning money, not playing for the country," he said.
"I still remember it was a great concern for us to get India out because they had quality batsmen like Rahul Dravid, Tendulkar, VVS Laxman and Sourav Ganguly. Within four days we couldn't get them out.
"But now, we get to see a side folding up before lunch as it lacks technique. They are interested in hitting the ball rather than concentrating on technique," he argued.
On chances of India winning the ongoing four-match Test series against Australia, Ranatunga said the hosts' prospects are decent as the touring side is weak.
"Without technique you cannot survive in Test cricket. India have very good hitters but they need to concentrate on technique," he said.
"Technique of first six Indian top batsmen, barring few, is abysmal. Australia, on the other hand, is an inexperienced side," he said.
Asked about Mahendra Singh Dhoni's captaincy, Ranatunga said nobody should comment on his leadership because he is the only Indian who has won two World Cups.
"I think India should allow Dhoni to captain," he said.
Ranatunga is considered the most successful captain of Sri Lanka, and it was under his leadership Sri Lanka won 1996 cricket world cup.