Super 8 film is known for its grainy, nostalgic look and vivid colors. The reason it's no longer sold in large film stores is because VHS camcorders, and then digital video cameras and cellular devices, replaced super 8 as the new home movie mediums. Digital videos are more pixelated when enlarged (blocky), but the videos are cheaper to film digitally and easier to store, as well as easier to carry around. For home movies, super 8 just couldn't compete with the digital technology available today.
This doesn't mean that super 8 is dead, though. Far from it, modern movies and television still uses super 8 film for its nostalgic look that digital technology can mimic but not genuinely portray. If you're into horror movies, you might have heard recently of the 2012 movie Sinister. Sinister was a horror film about a true crime writer who finds a stash of old super 8's in his attic, which belong to an inhuman serial killer. When Sinister was filmed, the producers opted to use real super 8 film stock to create the grainy effect of old 60's and 70's home movies.
Sinister's sequel is apparently coming out in 2015, during August.
If you're less into horror and would rather see the lighter side of what super 8 has been used to create, check out the intro to the 1988 show The Wonder Years. The Wonder Years was a sitcom about typical American family life. The intro features 'home movies' of the main characters.
More recently, in 2013, a London band that plays Seventies-style music, The Entrance Band, filmed an entire music video for one of their songs in super 8, with help from a really amazing group called pro8mm.
Pro8mm.com is a group dedicated to providing quality super 8 equipment, film stock, home video services and so-on to people who want super 8 or 16mm film to be available to them. This place is so cool, seriously, I thought super 8 cameras were fading out on eBay bids and stuff but pro8mm.com sells redesigned super 8 cameras! If you ever get the time, check this website out because it's really great.