There is a stigma attached to the show and its contestants. That is true.
However, all this show is, is a platform to allow you to go on to bigger and better things. This show guarantees that your first single becomes huge. After that, it is up to you (the singer), to work hard, make contacts and convince the right people that they should invest in you.
Also, the quality of your vocals do not dictate how successful you will be as a singer. There are many other qualities which dictate your level of success.
Lady gaga was one of (if not the) biggest selling artist of the last couple of years. She certainly doesn't have anywhere near the best voices on this planet.
The key is to first get yourself a record deal with a big company. You must then convince them to invest in you heavily. This means spending large sums of money on advertising your CDs and tour. It also means investing in your music videos. If you can get them to do this, then you stand a better chance of becoming "big".
It is still possible to become successful without the assistance of a big record company, but these days, this is rare.
As long as you finish in the top 3-4 on XFactor, providing you have convinced record bosses enough, you will stand a great chance of getting yourself a record contract and perhaps making it "big".
Katie is very interesting. It is clear that for whatever reason, she is not liked by the public. However, record company bosses seem to like her. So, they will sign her up and push her music upon the public very hard (in about 12 months time). This will be the acid test as to whether or not a record company can make someone who isn't liked by the public, a success.
I really do hope that Wagner wins this. That would be fantastic.