Your "Other" is high.
The backup stores all data not included with the sync process such as iPhone settings, SMS messages, notes, recent calls, call favorites, photos captured by your iPhone, 3rd party applications, and any data created and stored by 3rd party applications.
It should not take over an hour, not even close.
I suggest trying a Restore with iTunes.
The only content that is backed up is Other, which contains SMS messages, settings, email, internal and 3rd party application data, etc. Everything else is duplicated in other apps (iTunes, photo app, address book, calendar, etc). If you don't have a USB 2 port (only 1.1) that could explain why it is taking that long.
As suggested, try a Restore.
Even with a ton of apps installed, I believe your Other category is high.
Do a sync to update your iPhone's backup, and then try a Restore from your iPhone's backup. If this does not help, you may need to bite the bullet and Restore your iPhone as a new iPhone or not from your iPhone's backup.
I know with me mine typically took 5 to 10 min tops.
But this could very well be different from iPhone to iPhone based on the content you have and weather or not is local to the machine as well.
Also depending on your USB Port speed this can also affect the backing up process.
Also if you are doing other things on the machine that use other resources it can take those resources away from iTunes and slow backup process down.
But typical time 5 to 10 min average on most phones.
I can help you, SEARCH! I gave a solution several times already and this is going to be last time I;m repeating myself!
1. In iTunes go to File menu on top and click on "Transfer purchases from ..."
2. Go to Edit - Preferences - Sync, click on "Clear sync history", then delete all your backups from the list on top (bu selecting and clicking remove).
3. Sync your phone and patiently wait for it to backup, will take a while, you might think it didn't work, but after this new backup, you should notice the difference.
Just to be clear, some say it didn't work for them, but it helped me to get 30 seconds backups every time for 2 weeks now. All I do now is if I install new apps I transfer purchases again (and iTunes asks me to do so automatically).
Well I finally had to restore to pristine condition and then rebuild my iPhone from scratch. The most recent backup failed because it was corrupt. That was nice as I had a ton of info in Notes. So I went back event further and backed up from a really old backup and was able to get most of my notes back anyway. I then emailed each to myself and restored the 3G back to factory settings. At that point my "other" category was at about 200Mb's. I added all the apps I wanted performed a sync and now my Other is 648Mb's. If you all thought this was big before, now its even bigger and doesn't include any notes, SMS messages, app data, etc., because it's a brand new factory restore.
I've got my iPhone cord plugged directly into one of the USB ports on the back of my mid 2007 Aluminum iMac so I'm assuming it's USB 2.
I'm backing up now and if it continues at this pace it'll take about an hour.
I also have the same problem.
It got to the point to where I simply won't connect my phone to iTunes anymore!
Every time I connect it the phone wants to back up and it takes anywhere between 1 hour and 1.5 hours. Obviously, it will not sync unless you wait for the back up to complete!
I restored twice and it did not fix the problem.
Solution - turn backup off. Just means you will not have a backup to restore from but if you dont have a few hours to wait every time you need to restore the backup and up to an hour to wait every time you sync then you wont care.
Also this has been reported to help: