Maybe it's just nostalgia, I dunno – I was certainly getting flashbacks to being a twentysomething guy happily making a cartoon hedgehog run around while playing it – but Sonic 3 And Knuckles is still just a really cool game.
Let me tell you how cool this game is. Level two is the dreaded water level, which in a Sonic game is usually the most terror-inspiring level, as you're constantly at risk of drowning. Well, in the Hydrocity Zone, you can still drown if you're really working at it by trying to collect every single ring or something – but it's really more about tasting that familiar fear and overcoming it. And the game really emphasizes that, too; halfway through the level, you get funneled onto a series of ramps and loops and curves that accelerate Sonic to ludicrous speeds. Speeds so fast that he just casually runs across the surface of the water without breaking surface tension. And because the first time it happened you might have blinked, and were certainly going “wait did I just…?”, it then proceeds to do it again after some more general underwatery platforming. And the designers are so confident in themselves that they throw a moment like that away in the second level.
I guess in some ways you could say this was a turning point in the downfall of video games as a “test of skill”. But really, the Sonic games were never about hardcore skill at their hearts – anyone with a decent grounding in the language of platformers and a few hours to burn can probably make it to the bad ending of the previous games in a day or two. Sonic was always more about the feeling of being a cocky young god who cannot be harmed, and who looks wicked cool, and this is where they really started to realize this and put in lots of brief moments that existed solely to make you feel awesome.
It also tells its story very subtly. Just these little in-engine cutscenes, seamlessly integrated into the levels. No words, just pantomime and music and the occasional sound effect. But you very quickly know what's going on between Sonic and Knuckles.
And then every now and then it still says “hey screw you” and gives you a pain-in-the-butt boss. Like the level 2 boss. Man I hated that guy back when I was in my twenties and I still hate him in my forties, because he's just such a drawn-out, finicky fight.
It ain't perfect – its main flaw, IMHO, is that it's a little bit too long, due to its weird release as two interlinked games. It really would've fared better at about one and a half times the size of the previous Sonic games. But it's chock full of really delightful music and art, and level design that largely beckons you and says “hey let's go be totally awesome together”.
(It is also possible that I am simply an aging GenXer wallowing in nostalgia for her vanished youth. But I feel like most modern platformers I play aren't really saying much that S3&K hasn't already said, except with more words.)