It depends on how they are said. A difference in intonation can make all the difference in meaning. As a general rule if they are said more slowly they are more likely to mean the opposite.

I concede that those two words could be used ironically or sarcastically (like many others), but it would be presumptuous to suggest that they are always used in that sense. Use your common sense to determine if the context suggests such a meaning when you hear them, and don't be afraid of using them yourself when you truly want to express that something is interesting.

Just kidding!!!

Jin, this is REALLY an INTERESTING question!