Love Game Maker simply because it got me started and got me to where I am today. What I enjoy working with the most right now though is unity...I find it extremely easy to prototype with unity.
Yes there is no superior engine but I do understand you are just looking for a preference.
My very own game engine would be my favorite engine :-P It (nomlib) is my favorite primarily because of the fact that I know every square pixel of its codebase, thus I feel perfectly "at home" within.
To be fair: my other choice would be SFML and SDL.
A few of the strongest traits I desire in an API:
* simple and concise
* stay out of your way (I like the Unix philosophy of "doing one thing well" mentality, AKA modules/building blocks).
* written in C or C++
* open source or low-cost in terms of licensing
Unfortunately, my experience is still rather limited as I'm relatively new to gamedev.
Cheers!
