The main reason people feel as if there is nothing on the tube is the fact that we as humans have a short attention span. This translates to people switching from a channel once they become bored or disinterested. As they flip and they see nothing that really entice them they continue till they end up on the original channel in which they decided was boring the first place. The only people who think they have too many channels, are the ones who are engaged and have an attention span that keeps them glued to one channel.
With the growth of niche television channels, this eventually led to the growth of sub channels dedicated to things such as trout fishing and video games. This eventually led to there being a glut of channels in which only a few people were interested. For regular television watchers, this would add to the bane of them not having anything to watch because in their incessant flipping they end up in a patch of channels in which they have no interest in.
Have a large amount of channels is a good thing to some people but in reality less is better. If you only had a couple of channels, like people without cable or satellite television then you would be forced to watch whatever came on the TV. You would become adjusted to what channels show what show and create a viewing habit based off that. You would basically create your own TV viewing schedule and you would not stray from the fact that there is nothing to watch on television.
Downloading television programs is basically the same as downloading other kinds of files. You first need to find a website that contains links to TV shows online, and then you have to make sure that you have some kind of file-sharing client that will allow you to access the files (often called "torrents" after the name of one of the most popular clients out there). Television program files contain both audio and video components, so they are much larger than music files. As a result, it can often take several hours to download a single file.
There are a couple of different ways you can watch the files you've downloaded. First, the most common way to watch TV shows online is to simply view the downloaded file in a media player. You probably already have a media player on your computer; if you don't, there are several different ones that are available for free. You just have to run a search and choose the one that you think will suit you the best. You'll also have to download the appropriate codecs so that you can both see the video and hear the audio of the television program files. Again, a few minutes spent with your favorite search engine can point you in the right direction as far as codecs go.
If you're a bit more comfortable around your computer and know what you're doing, there's another way to watch TV shows online. You can actually burn the MPEG file to a CD-ROM (thus creating a VCD), which you can then watch on your regular DVD player. You should be aware that this extra step takes much longer and that not all DVD players are capable of handling VCDs. But the end result is definitely worth it, so give VCDs a shot.