Let's define underrated ---> movies that would rate below the median on IMDB - I.E. a rating of 6.5 or lower
I'll start it off (in no particular order)...
Bird on a Wire (5.9)
Young Guns (6.5)
Arachnophobia (6.4)
Air America (5.7)
Kindergarten Cop (6.1)
Crocodile Dundee (6.5)
Stakeout (6.5)
Judge Dredd (5.5)
The Cowboy Way (5.8)
SpaceCamp (5.6)
Always (6.4)