Don't look directly into its eyes!
I wasn't a kid who grew up watching Freddy and Jason. I was a huge comedy nerd, and was never a big fan of being terrified. I saw Poltergeist around age 10, and it was one of my very first horror films. I was scared just putting the VHS tape in the machine, but its rating calmed me down considerably. After all, how scary could a PG-rated movie be?
The answer? Extremely.
To me, Poltergeist is the perfect horror movie. It is genuinely scary, it is genuinely funny, and you genuinely care what happens to the characters. It's even got some dynamite commentary going on -- the television is full of evil! The genius of Poltergeist is that it takes the haunted house and plops it smack dab in the middle of suburbia. It's not a creepy Transylvanian mansion, it looks a lot like where most people grow up. The Freeling family looked a lot like my family, and that made it all the scarier. Like many Steven Spielberg films, Poltergeist juxtaposes the fantastical with the real in a way that the viewer doesn't doubt for a second.