Sorry to hear you're having this problem. Something is seriously wrong. Normally, a migration from one computer to another using Migration Assistant with a cable (I recommend a USB cable for speed and accuracy) connecting the two computers will not take over an hour or so. I suggest redoing the process. Be sure to carefully follow the instructions provided. Basically, the process is as follows.
You first begin by starting the process of setting up your new computer. You will be asked if you wish to transfer files. Respond YES and follow the instructions you will be given.
You will be told to turn both computers on and activate Migration Assistant in the old computer.
The computers should be connected with a USB cable to facilitate the transfer. Wi-Fi is simply not suited for a transfer of so much date and corruption often results. Do not use it. Ethernet works, but is slower.
You will be given several options as to what to transfer. You will likely want to transfer your settings and preferences.
You can transfer all or none of your files. You do not have an option to select certain files to transfer. If you wish to do that, then do so manually.
The old computer's operating system will not be transferred.
Allow for up to an hour for the transfer process to complete once you start it.
Enjoy your new Mac.
I hope this is helpful. Good luck.