Most underrated movie:
Pokemon: The Movie
Ok, seriously, all Kevin Smith movies, Chasing Amy was the best though, with Clerks a close second.
Spaceballs is waaaay up there, Buckaroo Banzai, Big Trouble in Little China was awesome, All of Jackie Chans earlier, Hong Kong movies were straight up hillarious, with kick anus action. Being John Malkavich(sp), though that was somewhat acclaimed.
Sticking with John Malkavich(sp), Rounders was also an underrated awesome movie. If you havent seen it, check it out.