Oh man oh man oh man I love Cuphead. I love classic animation; I love video games that are thoroughly happy being video games; Cuphead is both of those things. So much of the appeal to Cuphead seems so immediately obvious that I actually find it hard to put into words why I like it, so self-evident is it to me.
I guess the big thing for me is that Cuphead could have so easily excelled in one and one thing only. Would I have loved it if it were only a SHMUP without the graphics? Probably not, most SHMUPs need some sort of hook to draw me in. Would I have loved it if it were a graphics showcase without the tight gameplay? Probably, but I would mostly like it in the way I like something like Dragon's Lair in free play; a spectacle piece where substance is appreciated but not necessary. Here, the visuals are the draw, but you're as much here for the uncompromising gameplay that forces you to learn and overcome the challenges it offers, to adapt to the fights as they develop, and to always become a little better.
Cuphead is also a high water mark for how to handle references. You could theoretically go into this as your first exposure to video games or 30s animation and have a complete experience (though I do not imagine you'd get very far with this as your first video game). But the more you're familiar with either, the more cues you pick up on here and there. So many animations or visuals are pulled from classic Fleischer and Disney shorts; so many gameplay sequences are either direct pulls from or nods to late 80s/early 90s video games. Do you need to know that Ribby and Croaks' moveset references most of Street Fighter II's cast, or that the second phase of Djimmi the Great is a nod to Kirby Super Star's Heart of Nova? No, but it adds quite a bit to it. Likewise, knowing juuuuust how many things are nods to "Swing You Sinners" or Popeye adds quite a bit to those sequences. All of the game's fights still have their own personality, so the experience reads less like "Grim Matchstick is Wily's Mecha Dragon" and more like "Grim Matchstick is referencing Wily's Mecha Dragon" - a small but key distinction that makes the game its own thing.
The run & gun levels are probably the low point compared to everything else, but it's less that the run & gun levels are bad and more that the boss fights are so unilaterally great (something I think of as "the Muffin Problem"; given the choice between two otherwise identical muffins, you'd probably take the larger one, but that doesn't make the smaller one bad). There's something to be said for the process of grinding out and learning a platformer level as a pace-breaker among the standard boss levels, so their existence is certainly appreciated. I'm not entirely sure what you could do to make the levels as great as everything else, but there are at least solid hooks there (Funfair Fever's infectiously fun music, Funhouse Frazzle's gravity mechanics, etc).
I guess the big thing for me is that Cuphead could have so easily excelled in one and one thing only. Would I have loved it if it were only a SHMUP without the graphics? Probably not, most SHMUPs need some sort of hook to draw me in. Would I have loved it if it were a graphics showcase without the tight gameplay? Probably, but I would mostly like it in the way I like something like Dragon's Lair in free play; a spectacle piece where substance is appreciated but not necessary. Here, the visuals are the draw, but you're as much here for the uncompromising gameplay that forces you to learn and overcome the challenges it offers, to adapt to the fights as they develop, and to always become a little better.
Cuphead is also a high water mark for how to handle references. You could theoretically go into this as your first exposure to video games or 30s animation and have a complete experience (though I do not imagine you'd get very far with this as your first video game). But the more you're familiar with either, the more cues you pick up on here and there. So many animations or visuals are pulled from classic Fleischer and Disney shorts; so many gameplay sequences are either direct pulls from or nods to late 80s/early 90s video games. Do you need to know that Ribby and Croaks' moveset references most of Street Fighter II's cast, or that the second phase of Djimmi the Great is a nod to Kirby Super Star's Heart of Nova? No, but it adds quite a bit to it. Likewise, knowing juuuuust how many things are nods to "Swing You Sinners" or Popeye adds quite a bit to those sequences. All of the game's fights still have their own personality, so the experience reads less like "Grim Matchstick is Wily's Mecha Dragon" and more like "Grim Matchstick is referencing Wily's Mecha Dragon" - a small but key distinction that makes the game its own thing.
The run & gun levels are probably the low point compared to everything else, but it's less that the run & gun levels are bad and more that the boss fights are so unilaterally great (something I think of as "the Muffin Problem"; given the choice between two otherwise identical muffins, you'd probably take the larger one, but that doesn't make the smaller one bad). There's something to be said for the process of grinding out and learning a platformer level as a pace-breaker among the standard boss levels, so their existence is certainly appreciated. I'm not entirely sure what you could do to make the levels as great as everything else, but there are at least solid hooks there (Funfair Fever's infectiously fun music, Funhouse Frazzle's gravity mechanics, etc).