I’ll start out by saying that the 90’s was a great decade for movies. Some personal favorites include Galaxy Quest, the first two Toy Story movies, The Iron Giant, The Matrix, The Prince of Egypt, The Mask of Zorro, The Truman Show, Dark City…and that’s just movies from 1998 and '99.
Too keep this a bit more balanced, I’m not too crazy about a lot of popular music from the 90’s. IMO, Nirvana was the final nail in the coffin of rock music, at least as far as stuff that gets played on the radio goes. There have been plenty of good “niche” bands since, but not many that achieved widespread popularity. This was also the decade when rock-derived pop became very generic–in the early 80’s, there was a reasonable amount of experimentation because of the New Wave movement, but MTV and other factors largely killed that by the early 90’s. So because of all that, mainstream rock and pop have been stagnant since the 90’s.
Lastly, the 90’s were cool because they were the high point of Star Trek, at least in terms of popularity and the amount of content produced.