I think most people think the opposite of "like" is "dislike," but when I think about it, I don't think this is true.
"Dislike" actually means that one regards the thing of interest with displeasure. But the opposite of "like" should just be anything that doesn't mean "like" and in this case it could mean "dislike" but it could also mean that one is indifferent/neutral (neither like or dislike) regarding the thing of interest.
So what is actually the opposite of "like?"
This leads me to my next question on if "I don't like X" is the same as "I dislike X?" Based on what I alluded to above, I think the two are different. The think the former doesn't necessarily mean you dislike X, as I think it necessarily covers the case where you feel neutral about X, but I feel most people would interpret "I don't like" as "I dislike."