Likely the most popular catfish in the hobby today belongs to Cordoradinae group, also known as Corys. In this group there are at the moment 170 different species with more being discovered almost daily. What makes them so popular is their color patterns, intriguing habits, and their relatively ease of breeding.
Sizes for these guys range from less then an inch (2.5 cm) and go up to almost 4 inches (10 cm). A large majority of them are well-suited for aquarium life.
Now the Loricariidae group is another popular group that vary in size, color and form. The popularity of this group is due to the magnificent color patterns seen in many species. If you want a bizzare looking catfish then I recommend the small anchor catfish (Hara jerdoni), or try to Banjo catfish (Dysichthys coracoideus).
With so many species available, there is no doubt that you can maintain a lifelong interest is catfish as a whole.