Best caged pet?  

I guess I would say small birds. I know a lot of people like fish but they are messy and their tanks tend to smell bad. At least with small birds, it is fairly easy to clean out their cages.

I see lot of busy people have fish in their house. I think fish is a better choice than birds

Insects are probably the easiest. Things like hissing cockroaches and spiders. I know that is not for everyone though so keeping a smaller fish tank that is balanced (to be self-cleaning) is probably ideal.

Hamsters! 

I had one growing up and loved him. I named him Nibbler. He lived to be about 6 years old which is considered long for a small rodent. I have since wanted another one but never actually got one.

I mean to me, the best pet has to be one you can interact with and since cats and dogs are off the table, I would say the next best option is bunnies! They are technically "caged" though some people do train them to be free-roamers inside their homes. It just takes work but they still need to be crated at night. 

Fish are the easiest and more attractive. Second to them would be birds but they can be messy and loud so they are not for everyone.