I have been playing a lot of FTL lately. Which some people seem to consider a roguelike for some odd reason...  
 Well, it certainly has randomized content and permadeath! 

It's kind of funny, because these are really the two things that are most fundamental to why I got into roguelikes and why I still love some of them, and at least why think most of them are far more interesting than 99 % of the AAA titles. 
There were many discussions about 
permadeath, but in fact it actually just means that you can lose the game. And by extension that roguelikes really 
are games, because if you can't lose you're actually not even playing, you're either just 
experiencing something (like in all these AAA "press X to win" games) or solving a puzzle.
And 
input randomness is the other crucial quality of games. In a system without (effectively) random (i.e. 
uncertain) content you're not making decisions, you're just memorizing things. So, in a single-player game (which pretty much all roguelikes are) you have to have randomization to bring uncertainty into the system. (Many roguelikes also use 
output randomness to achieve that uncertainty, e.g. dice-rolling for attacks, which I'm definitely 
not a fan of...)
So these two things are really what 
I love about roguelikes. In fact, roguelikes are like this bastion of actual games in today's digital entertainment world. Granted, I've consequentially moved on to playing lots of board games now, but I still enjoy a good roguelike from time to time. Good to me means 
less stuff (e.g. loot, stats, bla) and 
more gameplay (e.g. positioning, skill usage, tactics in general). Sadly lots of "big" roguelikes are really heavy on the "stuff side" and overdo their randomization in ways unhealthy to the system itself. Therefore my favorites have become 
86856527, Shiren The Wanderer, Brogue, 100 Rogues, Zaga-33 and if you stretch the genre definitions a little also 
Desktop Dungeons.