Is it the same as with shit and the shit, i. e., if something is a bomb it sucks, is a failure etc. and if something is the bomb it's cool, awesome...?
I agree with jerry081958 but I would like to add that "a bomb" when used to refer to something that "sucks" is not a common slang expression, as far as I am aware. Instead, "a bomb" has a few particular uses I can think of:
If a movie is "a bomb" it is a bad movie, or it is unpoplar.
If a car is "a bomb" it is probably old and likely to break down.