The musical is another one of those evolving genres. Classic musicals are on the down-turn comparatively speaking, sure, if you are going the traditional route. I suppose you could now class musicals in two types: Musicals which have songs apart from the action, as a way of saying thoughts etc [ie the traditional musical style of 'I'll explain it with a song etc etc] or musicals in which music plays an important part in the story, but takes place as part of the action/story.
Modern day musicals are very much, like everything else I suppose, about selling soundtracks as well as movies. Your "Stomp the yard" type movies very much apply here, and you could even go so far as to say Glitter counts [hey I like it, but my tastes are a bit bitter
] They use modern music tracks in a way which doesn't take you out of the 'fantasy' like a traditional one does. Just think of any movie where music tracks are used as an important plot mover/intensifier and you'll see there's alot still around. Honey, Save The Last Dance, Bring it On, Centre Stage, Step Up, christ I could list a heap that use music in this way, and I would therefore count as a musical.
If you're talking the traditional sense, then they're still around, and made a semi comeback with things like Moulin Rouge, Chicago, Hairspray, High School Musical etc. Sure they're not as 'impacting' as the musicals of old, but still 'good' films.
The South Park boys are also great at the genre too, what with their work on Team America, The South Park Movie, even Baseketball and Orgasmo had their music in it in some form or another. They surely count as well.
But if you look close enough, many films use music to an important degree, with the musical montage as an important plot device [and a handy way to fill the soundtrack with a few easy to sell singles] from car racing scenes in Fast and Furious, to romantic movies which spawned hit singles.
Top Gun could even be classed as a musical, though loosely of course: the movie itself is pretty much dependent on its awesome 80s Loggins score. In my copies linear notes it even went on to say that Top Gun had a slow start sales wise, but the soundtrack was a big success, and from that success came people interested in seeing the movie based off the soundtrack.
The methodology of that has been applied, though I'm sure in not as strong away, to quite alot of movies you see lately.
Like Rev Powell said, there's not a lot of talent out there committing solely to the genre [though Baz Luhrmann seems to be having a bit of a crack with Moulin Rouge and Romeo and Juliet etc] and certainly not as much talent like your Gene Kelly's and Fred Astaires etc.
I'm sure they're out there, but I suppose the demand isn't as high, and boy is the market competitive.
I dunno...
But either way I'm a fan. They may be mostly sappy, but most of the time, even if the music sucks, I enjoy them.