The shows were broadcast in the mid-1960's and were popular hen, but nowhere near as popular as they are today. Today, Ultraman represents 1960's Japan kitsch and pop culture. It's not kids today who love Ultraman (today's kids like Poke-Mon); the people who like Ultraman today are in their 40's and older.
Anyhow, the best pat about Ultraman, I thought, was how he had to come from Outer Space to save the earth from all these silly monsters... The catch? he only had three minutes to do it every time. Isn't that hilarious?
Here is a selection of Ultra Monster illustrations done by Takayoshi Mizuki between 1965 and 1972.
If you want to see lots more Ultraman posters, go to Pink Tentacle: http://pinktentacle.com/2010/04/ultra-monster-art-by-takayoshi-mizuki/