Watch Under Siege obviously.
Bill and Ted, Speed and Point Break are the films that prove Keanu is not a terrible actor but one of the best of his generation.
Ghostbusters has aged very well apart from some sex pol stuff and the odd scene where Dan Ackroyd gets an unexplained, uncontextualised nosh off a sexy lady ghost.
Those plus the infamous and beautiful Abdul video:
Which was cut from the video I had off the telly for years before I got a DVD player. I don't remember that from seeing it in the cinema as a kid either, and I went three times. Lots of stuff in that film goes over your head as a child but reveals itself in later years. The script and performances add up to an ongoing and self-renewing miracle. I have never been bored watching it and I reckon I've done nearly 50 viewings since 1985.
I'm anti Bill Murray and he's fairly grotesque in this but for whatever reason it didn't spoi it for me.