Kudos to Cuphead, even when I die (like right at the fucking end of a boss fight, less than a millimeter away from the finish line, scream) the game is so appealing and detailed that the bosses are a joy to replay. The animation, the music, the sound effects, the backgrounds... so goddamn good. I find myself tapping my feet along to the music quite a bit. The super fast reset from dying helps so much, too.
Also, showing how far you've progressed with a boss or level is such a clever idea. It's that tantalizing look how close you were! or look how much further you got that time! It makes me so much more likely to retry, instead of taking a break or going to try another boss.
It's always a wonderful thing when an itch to keep playing a game stays with you, or digs its claws into you to the point you're ruminating on it when you should be doing other things, ie, in the middle of dinner with an epiphany of, 'oh, that's how I can dodge that attack!'