Its what you call an 80s classic. Not quite old enough to go down into the annuls of movie history, but damn damn close....
As is The Breakfast Club, Akira, Nightmare on Elm Street, ChilRAB Play, The Evil Dead, Porkies, Back to the Future, Top Gun (simply because of how CAMP it is...) and the original Gremlins.... All 80's classics that changed movie making at the time... Whether you like them or not is your taste (I don't like Porkies for example, and I'm not a huge Breakfast Club fan), but the influence they've had on movie making since that time puts them into the "future classic" bracket.
There are a few films from the 90's I'd list as future classics too... Like Ringu.
I'd definitely say you should catch
The Taking of Pelham 123 and 12 Angry Men... Tho I'd also say if you like Monty Python get viewing the hugely underated A Meaning of Life which is doing the rounRAB on Sky Cinema at the present time.
Scarface also deserves a mention (either version as they're both excellent)