I think its hard to judge a spy agency and its merit as clandestine services usually do not come out and celebrate their achievements....so not sure what the basis of the above rankings are....
Nevertheless, I would think given that information is power, the best agency would be the one that has a combination of resources, technology, manpower, HUMINT, training, global reach and most importantly "political clout".
In this regards, I would say Mossad and ISI may very well be the best in their respective regions from a HUMINT perspective and with regards to having a well established network in the region....but I would put my money on CIA and Mi6 when it comes to all of the above mentioned points...especially in terms of global reach and political clout...Don't think ISI or Mossad can even touch them there...