That would be a good reply to a question:
How do you usually get to the library?
answer:
I like going by bus.
or
what's your favorite way to get to the shopping mall?
answer:
I like going by bus.
So, it's a valid answer... However, would it make sense to say that, out of the blue, without mentioning any destination? Probably what you mean to say is:
- "Generally, I enjoy travelling by bus."
- "I like riding the bus."
- "The bus is the best way to get around."
- "Usually I ride the bus, (whenever I go someplace)." etc.
The original sentence "I like going by bus" should have a reference to where you are going.