Intelligence can be measure in so many ways. According to animal planet, there are six breeds that have the highest level of inteligence:
Balinese, Bengal, Colorpointe Shorthair, havan Brown, Javanese, Oriental, Siamese, Sphynx
However, its the combination of the other atributes that determines how "intelligent" a human determines the cat is. I have a bengal, and I can say this cat is like having a puppy. He constantly wants to play, but is also very lovable. He sleeps between my wife and I every night. He knows when it's bed time. He knows where all his toys are, he knows his name (will meow at you when you call his name). i have known a few Orientals and Siamese, and they are definately not as "compatible" with humans as Begals. Our cat will always be in the same room as us, and never hides under beds or in closets, and loves company. however, it is strongly advisable to not allow bengals to be outdoor cats as their instincts will kick in, and it would be very difficult to domesticate them again.