Musukogoji, that is a matter of opinion -- I personally like it very much, because it was different from the other Toho Godzilla posters; it was a painting, rather than a photo-collage. But to clarify, there are TWO posters for BIONIC MONSTER, one that employs the original Toho poster art, and the second which uses Basil Gogos' fantastic painting that appeared on the cover of Famous Monsters of Filmland magazine. This art was also used on the subsequent COSMIC MONSTER poster.
Also, there are versions of the first BIONIC MONSTER poster (with the Toho art) that simply had the new COSMIC MONSTER title PASTED over the offending title! Back in 1979, I saw this for sale at a movie poster shop in San Francisco, but someone had already bought it before me. Years later, I found an unmolested original.
Peace!