No unreal there? Even with those game engines you will still find you are writing functions and behaviors making your own libraries and the such like you would anywhere else. They key thing is they to some heave lifting for you like physics and setting up many things that have to to with fast rendering. They also have editors to help with level creating which I think is the BIGGEST advantage. Most people on here are tinkerers and would rather tinkerer with whatever they are working on than using some else s code. I know a lot of people who use unity. I have tried it and just can't get into it most likely due to make lack of experience.
Cheaters way of making games?
hmm...skyrim the Havoc physics lib which I don't think they created and probably many others. Virtually every COD runs on some engine which will have libs not made by the main devs. Put simply, no it is not cheating in the slightest. As Heroes said, there is a bunch of stuff that goes into developing a game and so any time that can be cut writing in house tools is a plus. If you are really serious about developing a game, use an engine and get a team going.
I personally hate Game Maker since it teaches you practically nothing, and all these kids are running around showing off their games made in it and saying they are the next Notch, it just pisses me off more than anything.
He made one big game...John Carmack would be a better reference.
Edit: Blah meant Carmack