I wouldn't say that all pre-builts are bad.
A pre-built gaming computer is definitely a poor value though.
OP, I would recommend you consider returning your purchase and do a little more research into what is required to build a computer. You can easily save yourself several hundred dollars.......
I built my gaming PC in 2008 with zero experience building computers. I got all of my information from this board and these members. I'm sure even PP Mguire was involved at some point in the process.
BUT If you're okay with the computer you've purchased, then by all means keep it and use it. I'm sure it's got a great warranty to go with it should anything go wrong and even though it's pre-built, you can still upgrade it in the future should you wish to add ram, SDDs, gfx cards, etc. Just be aware that you have grossly overpaid for it.