We cant find out which is the best intelligence agency in the world.All intelligence has its own achievments and embarrassment.
CIA is largest agency in the world.But their quality of intel is now in question causes are several .9/11 is the best example.they simply ignore massoud warning.Iraq war ,present Snowden issue also show its incompetency.But CIA is powerful because US is a superpower.
same goes to ISI. their best intelligence operation is they can influence Taliban and most of terrorists group in the world and they run a largest network in India. Counterfeit currency also it operation against India.ISI intel quality problem arise in 1971 ,1998 India nuke test and 1999 kargil war,26/11 is their best operation but cant anticipate diplomatic fall out .But their main disadvantages is ISI dont use high technology .CIA is light years ahead in that case.
RAW has it own achievements and losses.1971 war ,Operation meghdoot,1989 anti -insurgency measures,1974 and 1998 nuke tests ,Operation leech etc are their achievements.Losses are 1999 kargil war cant findout pak troop movements. numerous terrorists attack in India.May I K Gujral folly cause a lot of damages to us.Indian friends may know about that.Technology is also a problem for India's agency .But RAW facilities is considerably better than ISI.RAW has most advanced satellite surveillance and other equipments.After 26/11 their caliber substantially increased.But it is still far behind than CIA.
At a certain extent MOSSAD is the best intelligence agency in the world .Several reasons .Most example is their is no single terrorists attack inside Israel .US,India and Pakistan suffer terrorists attack inside their country in different magnitude and numbers.All previous war of Israel, decisively won by Israel.Still they can leak any information in this world.Technology of Israel is better.Sometimes even US cant understand their method.But they have also embarrassment ,Jonathan Pollard issue and
arrest of Israel agents for targeted killing.But they are still better than other countries.