http://bisqwit.iki.fi/nesvideos/
This website is an archive of tool-assisted speedruns on old school games like contra, mario, etc. They have some newer stuff like GBA runs as well. All the files are available for download by torrent, if you have good bandwidth, or you can usually download the emulator's movie file which is infinitely smaller and re-creates the movie through recorded inputs (obviously you'll need to download the emulator and roms to watch them that way, but the quality is much perfect and the filesize is way smaller on the download).
This website uses torrents to download the movie files, so I reccomend a good torrent program such as Azereus.
I reccomend the 9 minute Contra run, 10 minute Mario 3 run, the Megaman 2 run and the 9 minute River City Ransom run. There are many other great movies too, check the page out.